[CentOS] Sharing virtualizing physical Server 2008R2 experience on CentOS 7

[Emmanuel Noobadmin]

Not as smooth an experience as I had assumed it would be after a test
run with a clean install worked perfectly. So figured I would share
the experience in case anybody else runs into similar situation since
not all information are consolidated in a single place.

Physical machine in question is a 4yr W2008R2 server (non-raided!)
running custom app from defunct developer which is why I am
virtualizing the failing server instead of doing a fresh/newer Windows
setup.

Too many articles online saying can't just dd/clone a Windows drives
and expect it to run. So opted to go with the "new" Bare Metal Restore
functionality added in 2008R2.
https://blogs.technet.microsoft.com/askcore/2011/05/12/bare-metal-restore/



BMR caveats
==
- It can only restore from BIOS to BIOS and UEFI to UEFI (virt-manager
in C7 doesn't appear to do UEFI, see below)

- It can only restore to a disk of same or larger size.

- It doesn't appear to be possible to trick it using a sparse qcow2
disk file to fit it into a smaller disk (500GB HDD to 250GB SSD in my
case)



UEFI

- current version of libvirt/virt-manager in C7 doesn't appear come
with UEFI firmware/loader

- got it done thanks to http://www.nbalonso.com/centos-7-uefi-boot-kvm/

- Summary:
  - install ovmf from https://www.kraxel.org/repos/
  - using virsh edit, add to the  section:
/usr/share/edk2.git/ovmf-x64/OVMF_CODE-pure-efi.fd

- sidenote: with the UEFI BIOS, warm reboot of the VM often ends up in
an UEFI shell instead of booting directly, and sometimes the shell
doesn't see attached drives. A "cold" reboot of the VM will fix this.



Registry changes before booting
===
After using the S2008R2 installation ISO to do a BMR restore, the
restored S2008R2 won't boot.

- need to boot into recovery mode with the CD again to run regedit to
change some registry keys (
http://tech-stuff.org/migrate-windows-2008-server-from-physical-to-virtual-environment-or-to-different-hardware/
)

- specifically for S2008R2
  - select HKLM then open the File menu to 'Load Hive' from \restored
drive\Windows\system32\config\SYSTEM. Give it a name e.g.
'restored_HLKM'
  - navigate through the restored HKLM tree to \ControlSet001\services
and set the following for KVM
  - intelide > start = 0
  - lsi_sas > start = 4
  - msahci > start = 0
  - pciide > start = 4
  - the actual value in my registry are 3 instead of 4 but the changes
appear to work regardless.

- Note: I'm using IDE not virtio mode to avoid any added complications.


Multi-core issue

For some reason, the restored VM won't boot if more than 1 core is
assigned. There are plenty of hits on this issue but unfortunately
mostly related to attempts to do PCI VGA passthrough. Trying out the
various suggestions such as emulating core2duo, requiring nx and such
did not really helped. What worked in the end is
- single core
- remove  section in the guest xml
- core2duo (might not be necessary)
- require nx (might not be necessary)



Resizing drives
===
In my situation, the server barely used 60GB on the old drive across
two partitions. So 250GB SSDs was assumed to be enough until I hit the
BMR restore issue. Ended up using a temporary 1TB spare drive to
install before trying to shrink it down to fit onto a 250GB SSD.

- Windows Disk Manager won't resize boot partition below 1/2 of original

- Do NOT use Aomei partition assistant (thought it was easier and
safer to use a Windows-based tool for this but...)

- gparted livecd won't boot properly in KVM with UEFI/OVMF so better
to just use it on a raw disk on the virtualization host directly.

- Before repartitioning, from here
https://wiki.archlinux.org/index.php/GParted (although says it's for
WinXP)
  - Delete the registry key HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

- randomly gparted will get errors:
  - about unable to read data on the ntfs partition, fixed by mounting
the partition before running gparted.
  - or abort a resize/move operation because it can't find the device
in /etc/mtab. It doesn't quite make sense to me because the partition
seems to appear only in /etc/mtab if I mount it in the host. But if I
mount the drive, gparted will indicate it is mounted and needs to be
unmounted. Fixed by rebooting the host machine everytime it happens.

- Windows still won't boot after partition changes despite deleting
the registry key. Fixed by manually running chkdsk /f in Windows
rescue/repair command prompt. No errors found but for some reason this
makes Windows happy.



Transferring to smaller drive

The web is full of warnings about trying to clone a bigger drive into
a smaller drive using dd. Especially since GPT puts a spare table at
the end of the drive. However, I figured it can't hurt to try since I
will still have the working 1TB to fall back on.

- did a dd if=/dev/vg/lv_temp of=/dev/vg_ssd/lv_ssd1 BS=32M conv=notrunc,sync

- appears to work as Windows booted without complains.

I'm still left with the 

Re: [CentOS] Any experiences with newer WD Red drives?

[Emmanuel Noobadmin]

On 3/2/16, m.r...@5-cent.us  wrote:
> Sorry, we don't seem to have any Supermicros with that m/b, but with the
> ones we have (all X9* m/bs), as well as our many Dells, old Penguins
> (rebranded Supermicro), and HPs, we've had no trouble at all with them,
> other than the occasional one that dies.

I haven't had any problems with past Reds on the X9* and X10* boards
we used before as well. This was the first time we are using the X11
board with the new chipset, so I was wondering if that might have a
part to play.
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Re: [CentOS] Any experiences with newer WD Red drives?

[Emmanuel Noobadmin]

On 3/2/16, John R Pierce  wrote:

> any chance your SATA cables aren't up to SATA3 (6gbps) performance levels ?

The cables came with the SuperMicro board so I certainly hope they
haven't started cheapening out on those :D

In any case, the cables shouldn't be the problem because I swapped
other drives (SSD and HSGT HDD) into the same drive bay, swapped
cables as well as put the Red into 3 different drive bays/SATA
cables/ports without any improvement. Both the SSDs I tried were able
to hit around 450Mbps sequential write speed which is around the
general ballpark performance from online sites so that should
eliminate cabling/connection as the source.
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Re: [CentOS] Any experiences with newer WD Red drives?

[Emmanuel Noobadmin]

On 3/2/16, Alice Wonder  wrote:
> Is it possible to build a vanilla kernel to boot from and test if same
> issue exists?

Unfortunately no, had to get the server out ASAP so already swapped
the Reds with the vendor for HGSTs.
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[CentOS] Any experiences with newer WD Red drives?

[Emmanuel Noobadmin]

Might be slightly OT as it isn't necessarily a CentOS related issue.

I've been using WD Reds as mdraid components which worked pretty well
for non-IOPS intensive workloads.

However, the latest C7 server I built, ran into problems with them on
on a Intel C236 board (SuperMicro X11SSH) with tons of "ata bus error
write fpdma queued". Googling on it threw up old suggestions to limit
SATA link speed to 1.5Gbps using libata.force boot options and/or
noncq. Lowering the link speed helped to reduce the frequency of the
errors (from not getting a smartctl output to getting a complete
listing within 2 tries).

Tried two Reds produced in Jan 2016, two HGST, two SSDs on the same
combination of cable/bay/SATA port as well as different combos. SSD
maxed out at 450Mbps dd write test so doesn't appear to be lousy
cables or board problem. Basically only the Reds were having problems.

Strange thing is a netinstall of CentOS 7.0 "minimal" worked with one
of the Reds before starting to cough. Now that I think about it, could
be due to an update to 7.2 after installing.

Needed to get the server out the door ASAP so didn't have time to try
C6 once I confirmed it was the drive and promptly replaced it with
another HGST.

Since I'm likely to use Reds again, it is a bit of a concern. So
wondering if I just happen to get an unlucky batch, or is there some
incompatibility between the Reds and the Intel C236 chipset, or
between Red / C236 / Centos 7 combo or the unlikely chance WD has
decided to do something with the firmware to make them work on on NAS
and not workstation/server chipsets to make people buy better stuff.

Anybody has recent experiences with them recently on the same chipset with C7?
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[CentOS] Recovering LVM after crash

[Emmanuel Noobadmin]

I've been trying to cover data from a disk that appeared to had been
corrupted after a power outage. The original setup was lvm on md raid
1 which appears to be what is complicating the issue. Apart from
/boot, everything was on LVM partitions so I don't have any backup lvm
information.

Following various guides online, I've recreated duplicated the raid
partition with dd onto a new disk, recreated the raid 1 array with
missing device, but the pv cannot be found.

I've tried to find the lvm uuid using this guide
https://www.howtoforge.com/recover_data_from_raid_lvm_partitions but
despite dumping twice the data to file, there are no plain text
configuration information. The drives are not encrypted so that isn't
likely to be the problem.

I also used testdisk to try to recover the partitions but it says they
cannot be recovered. During analysis, it was able to detect the lvm
partitions, extracted output:
Linux LVM  1069 146 38 60799 228 29 959567608
Linux  1069 179  7 57740  22 10  910409728
Linux  790  66 45 59780 237 33  947685112
Linux  1069 179  7 57740  22 10  910409728
Linux  29283 103  5 85953 201  8  910409728
Linux  29292 181 10 85963  24 13  910409728

The numbers are start CHS, end CHS and size in sectors. There seems to
be way more possible partitions than there should be, possibly results
of previous LV resizing.

With only such data left, is there any possible way to reconstruct the
PV/VG/LV without the uuid and recover data?
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[CentOS] CUPS Print job inverts colours halfway

[Emmanuel Noobadmin]

I have two Canon printers a MF4720W and LBP7100Cw. Previously a PC
running CentOS 6 were able to print without problems via network.
Unfortunately the hard disk died and in replacing it, we also upgraded
to CentOS 7.

Now the problem is that a test print to either printers looks OK for
the first half then inverts colours for the second half. i.e black
text on white background becomes white text on black background.

After testing via printing from LibreOffice, printing PDFs and
printing from browser, it appears that the problem is triggered by
having graphics in the document. For example, if we print a page with
a logo at the top, the problem occurs. But if we edit the same
document so that the logo is at the bottom, we don't encounter this
problem.

Having different fonts on the page does not appear to trigger the bug
as pages with multiple fonts but no graphics have no problems.

The only error in the log is repeatedly this:
CreateProfile failed:
org.freedesktop.ColorManager.AlreadyExists:profile id
'Canon-MF4700-Series-Gray..' already exists

Googling for the error turns up a lot of hits but mostly for Ubuntu
and USB connected Brother printers. I've tried some of the suggestions
where it might appear relevant such as changing LANG to en_US and
reinstalling CUPS but nothing has helped so far.

Canon drivers used are from
- Linux_UFRIILT_PrinterDriver_V110_uk_EN (LBP7100Cw)
- Linux_UFRII_PrinterDriver_V300_uk_EN (MF4720w)
which provides
- cndrvcups-common-3.10-1.x86_64.rpm
- cndrvcups-ufr2-uk-3.00-1.x86_64.rpm
- cndrvcups-ufr2lt-uk-1.10-1.x86_64.rpm

CUPS version is cups-1.6.3-17.el7.x86_64

Please advise what else can I do to narrow down the issue or fix it?
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Re: [CentOS] CentOS 6, CUPS and Canon printers problem

[Emmanuel Noobadmin]

Just to follow up to myself and leave a record, the problem is SELinux
blocking the driver from creating/reading/writing temporary files
under CUPS.
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[CentOS] CentOS 6, CUPS and Canon printers problem

[Emmanuel Noobadmin]

I was trying to get a new Canon laser printer LBP-7110CW to work with
a CentOS 6 machine. It already has an older Canon multi-function laser
MF-4720W which worked fine. Both printers are connected via wireless.

The new printer works fine from a Windows machine. The web-based GUI
can be accessed from the C6 machine without problem either. However,
CUPS cannot discover the printer when adding a new printer although
it could probe it successfully if I provide the IP address. Neither
could the Canon provided cnnst application find the printer on its
own.

This appeared to be related to iptables since it would discover the
printer if I disable iptables. I assume the discovery is done by SNMP
so it is a little odd why iptables have to be disabled for the C6
machine to find the printer which is the server so to speak.

Ignoring that, the new printer still cannot print after being added. A
process c3pldrv gets stuck at 100% cpu utilization when a print job is
sent. A new c3pldrv process will spawn for each print job and remain
for hours if I don't manually kill it.

Throughout this time, the printer can be accessed via its web
management gui from the same machine and there is no problem printing
to the older multi-function printer. So network connectivity doesn't
appear to the problem.

It also doesn't make a difference whether I set CUPS to use raw socket or lpd.

The C6 system was updated to the latest files and the latest UFR-II
drivers from Canon was downloaded and installed.

Anybody has any experience or clue about what might be the problem?
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[CentOS] Excluding block device from mdadm scan at boot

[Emmanuel Noobadmin]

Using Centos 6, how to I prevent mdadm from assembling arrays from
specific block devices at boot?

Background:
Due to an accident, one of my servers went down and on reboot, got
stuck first at NFS statd, then at automount after I disable NFS in
single user mode. Only after disabling autofs was the server able to
complete booting into runlevel 3.

On investigation, it seems that mdadm added two new raid devices md126
and md127 assembled into read-only in degraded raid 1 mode from two
unknown device dm-20 and dm-8. My guess is that automount was trying
to mount these devices which caused the boot process to fail.

After doing some googling, I found the lsblk command and was able to
identify dm-20 and dm-8 to be RAID devices created from two lvm
logical volumes. These were added to virtual guests as raid devices
using whole drives instead of partitioned raid.

Unfortunately, I had been unable to find out if it was possible to
tell mdadm not to include these drives, the mdadm.conf manpage doesn't
appear to list any such option. Is there some way to achieve this or
is permanently disabling autofs my only option?
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Re: [CentOS] Need to Understand booting process of CENTOS-7

[Emmanuel Noobadmin]

On 10/3/14, Timothy Murphy gayle...@alice.it wrote:
 m.r...@5-cent.us wrote:

 Geez! I bet he didn't think that he'd have to add sarcasm/sarcasm
 around that I've lost track of who posted that, but *I* thought it
 was
 funny

 Why send a smartass reply to a simple query?

I'd admit to a certain level of personal bias and snappish mood when I
wrote that reply, due in part to the fact the OP's name and style
comes across as similar to somebody I had to deal with earlier,
although I still lean, perhaps unfairly, that he is that same sort.
Guys with very impressive (and frequently to the point of being
absurd) resume/credentials who don't actually know shit about the work
they need to do, then try to leech off others (esp colleagues) and
pass off as their own work for credit.

Usually, I'm more than happy to share what I know, especially since
much of what I learnt are from the efforts of others, but when it
comes to this sort who don't even bother to show the slightest effort,
I like tripping them up :)
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Re: [CentOS] Centos laptop support

[Emmanuel Noobadmin]

On 10/4/14, Phil Wyett philwy...@aura-tech-systems.co.uk wrote:

 My intention is to run CentOS 6.x and VM Windows and any other OS etc.
 After discarding many options I seem to have settled with an eye on a HP
 ProBook 455 G2.

 http://store.hp.com/UKStore/Merch/Product.aspx?id=G6W43EAopt=ABUsel=PBNB

 This system has legacy BIOS options if you read the manuals and does
 mention linux quite a bit. There is info about Ubuntu and below is a
 link to the laptop on Ubuntu certification site.

 http://www.ubuntu.com/certification/hardware/201404-14968/components/

 If anyone is running CentOS on this series of laptop, I would very much
 like to hear your experiences!

I don't run C6 on this series but having tried both C6 and C7 on a HP
Touchsmart with AMD/ATI GPU, my suggestion echos others in the thread,
stay away from AMD graphics for laptops. C7 works fine, once I got
proprietary AMD drivers installed and remembered to recompile them
after a kernel version jump.
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Re: [CentOS] Need to Understand booting process of CENTOS-7

[Emmanuel Noobadmin]

On 10/1/14, keshab mahapatra ping2...@gmail.com wrote:
 Team,

 could some help me understand the booting process of CENTOS-7

 I need to have constructive material where i could able present a
 presentation on booting process of CENTOS-7

It's very simple actually. The first step in the booting process of
CENTOS-7 is the application of emf to the system, following which it
would initiate the cmos process to load the GPT from disk and hand
over to LILO which will bootstrap the kernel from the file allocation
table into the high memory area before running systemd to complete the
booting process.
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Re: [CentOS] Troubleshooting suspend/resume problem in Centos 7

[Emmanuel Noobadmin]

 In the meantime, I'm going to try the suggestion of using Catalyst
 drivers first before venturing into kernel building since the laptop's
 graphics is behaving oddly apart from the resume problem.

As an update, downloading the latest AMD fglrx 14.4rev2 drivers and
installing it fixed the unable to resume problem to some extend.
pm-hibernate will work properly but pm-suspend will wake up to a blank
screen which apparently is a common enough problem from googling.
Might be something to do with systemd based on this archlinux thread
https://bbs.archlinux.org/viewtopic.php?id=178450

However, in my case, this appears to be circumvented in runlevel 5
(runlevel 3 gets stuck until I type blind or ssh in to
reboot/hibernate the machine). In runlevel 5, the screen flashes on
briefly, then go blank, after a while it comes back and abrt reports a
crash with plymouthd. Seems like X will retry in this situation so it
causes the display to come back.

If it is of any use, I could send the abrt report somewhere.
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[CentOS] Troubleshooting suspend/resume problem in Centos 7

[Emmanuel Noobadmin]

I'm trying out CentOS 7 using a HP AMD laptop
http://h10025.www1.hp.com/ewfrf/wc/document?cc=uklc=endocname=c03877039

The problem is the laptop doesn't suspend properly in runlevel 5 /
graphical.target and following guides, I found that it suspends (power
LED blinking) but does not resume in runlevel 3 / multi-user.target.
When it locks up, the machine is unresponsive to ping/ssh so it's not
just a blank screen.

Unfortunately, the only applicable guide I found on troubleshooting
this is for Ubuntu, which requires the kernel to support pm_trace
which isn't found in /sys/power.

Since there is a big red warning on centos.org about
building/compiling my own kernel to add functions, I'm wondering if
there are any alternative method to troubleshoot the issue on CentOS.

I suspect it may be related to the Radeon GPU as I notice that every
now and then after fresh boot, the GUI desktop will freeze for a while
and dmesg will contain errors:
[drm:cik_ib_test] *ERROR* radeon: fence wait failed (-35)
[drm:radeon_ib_ring_tests] *ERROR* radeon: failed testing IB on ring 2 (-35)

As a side note, this laptop had no problems with suspend/resume when
it was running Ubuntu 14.04
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Re: [CentOS] Troubleshooting suspend/resume problem in Centos 7

[Emmanuel Noobadmin]

On 7/16/14, Karanbir Singh mail-li...@karan.org wrote:
 file an RFE for the centos-plus kernel, maybe we can get this in there ?
 Otherwise, nothing really stops you from building your own kernel for
 your own machine :)

Filed.

In the meantime, I'm going to try the suggestion of using Catalyst
drivers first before venturing into kernel building since the laptop's
graphics is behaving oddly apart from the resume problem.
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Re: [CentOS] Repodata filename problem in CentOS-6.5-x86_64-bin-DVD1.iso ?

[Emmanuel Noobadmin]

On 1/25/14, Johnny Hughes joh...@centos.org wrote:
 dd if=CentOS-6.5-x86_64-bin-DVD1.iso of=/dev/sdc

 Then boot from the usb key.

 Obviously there is some issue the extraction process on the filesystem /
 os you are using and the loop mount and / or the livecd creator you are
 using ... as our ISOs do install and the files are named properly on
 them to get them to install.

Thanks for pointing out that possibility. The Fedora LiveUSB creator
previously worked for a C6.5 LiveCD to HDD install so it never
occurred to me that the problem was in that direction. Using the dd
method on another CentOS machine with the same ISO worked so it looks
like some kind of limitation on Win7 instead.
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Re: [CentOS] Installing on USB Flash Drive

[Emmanuel Noobadmin]

On 1/25/14, Matt matt.mailingli...@gmail.com wrote:
 Is it possible to install CentOS on a USB Flash Drive.  Have boot
 sector, / and /boot on USB drive then put /home, etc on a software
 raid array of the physical drives.

 Thought there used to be motherboards with SDHC slots that you could
 use to boot off.

I have a couple of machines that run entirely off USB drives with
mdraid so I'd say it's possible, barring any unusual hardware
compatibility issues.

However, note that there might be an issue with anaconda and big USB
storage. The boot partition anaconda creates will not boot past grub.
I needed to manually create the partition to start on sector 63 for
grub to see it. Happens on my 16GB sticks but not on small 1GB sticks.
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Re: [CentOS] Problem installing Centos 6.4/6.5 from USB stick seen as HDD by BIOS

[Emmanuel Noobadmin]

On 1/23/14, Steve Clark scl...@netwolves.com wrote:

 can you use -o remount in the mount command?

For some odd reason, my current attempt to do this had no problem
mounting the install USB drive. Which then led me to realize that the
problem is something else.

After figuring out where anaconda keeps log, I found that the error
isn't that it couldn't find the drive. Rather, it couldn't find the
file:

media/repodata/0dafccfdbf892f02acca8267ade4bdcee7280a682e65dc7e29145f3341fd7a8c-primary.sqlite.bz2

(the target machine doesn't have network so there might be typo in the
filename due to manual copy)

listing the USB drive shows that the repodata directory has the file
BUT missing the -primary.sqlite.bz2 extension. In fact, none of the
human-unfriendly file names have any extension. In case it was an
error transferrring the ISO to USB, I checked the ISO and found that
the repodata directory appears the same.

In comparison, browsing online mirrors such as
http://ftp.linux.ncsu.edu/pub/CentOS/6.5/os/x86_64/repodata/ shows all
the similar looking files have extensions.

But the ISO's md5/sha1 checksums are correct.

Based on the information in TRANS.TBL, I added the extensions to the
files and anaconda was able to proceed to the package selection.

I will start a new email to check if there is a problem with the ISO on mirrors.
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[CentOS] Repodata filename problem in CentOS-6.5-x86_64-bin-DVD1.iso ?

[Emmanuel Noobadmin]

Originally posted as Problem installing Centos 6.4/6.5 from USB stick
seen as HDD by BIOS

Further testing seems to indicate there is some odd issue with the
file names in the repodata directory.

During installation, after the partitioning stage, anaconda logs an
error trying to access the file
repodata/0dafccfdbf892f02acca8267ade4bdcee7280a682e65dc7e29145f3341fd7a8c-primary.sqlite.bz2

checking the USB drive as well as the downloaded ISO shows that the
file is named
repodata/0dafccfdbf892f02acca8267ade4bdcee7280a682e65dc7e29145f3341fd7a8c

It seems that the filenames are truncated after the first dash e.g.
b4e0b9342ef85d3059ff095fa7f140f654c2cb492837de689a58c581207d9632 should be
b4e0b9342ef85d3059ff095fa7f140f654c2cb492837de689a58c581207d9632-c6-x86_64-comps.xml

Renaming the files on the USB drive according to the information in
repodata/TRANS.TBL appear to fix the problem and anaconda was able to
proceed to package selection.

The DVD ISO checksum is correct. I also compared the checksum files
from another server in case the mirror I used had an outdated/bad
version.

Is the problem with the ISO, or is anaconda supposed to had figured
out the filename based on TRANS.TBL but not doing so.

The problem originally started with a C6.4 install but I've wiped that
ISO so am unable to verify if the cause is the same.
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Re: [CentOS] Repodata filename problem in CentOS-6.5-x86_64-bin-DVD1.iso ?

[Emmanuel Noobadmin]

On 1/23/14, John Doe jd...@yahoo.com wrote:
 I did not follow the previous thread but are you putting the iso file on the
 key or are you extracting the iso content to a folder on the key...?

USB drive was created using Fedora's LiveUSB Creator which I believe
extracts the ISO content. However, viewing the original ISO shows the
filenames are already truncated, so I don't think it would had made a
difference if the ISO was placed on disk or extracted.
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[CentOS] Problem installing Centos 6.4/6.5 from USB stick seen as HDD by BIOS

[Emmanuel Noobadmin]

I'm trying to install C6.5 on a USB stick (created using Fedora
LiveUSB Creator).

The problem is the machine using an Intel ITX board sets the USB stick
as a HDD instead of a CDROM. During install, the DVD couldn't find the
installer automatically and I must choose the HDD option for it to
proceed to network/timezone/storage setup.

After the storage partitioning, it will throw an error that it is
unable to read package metadata. Although there is an option to edit
the repo information, there isn't an option to specify a hard disk.

Switching to console, attempts to mount /dev/sdb as /dev/cdrom or
/mnt/sr0 met with failure because the USB drive is in use.

Previously I used 6.4 and downloaded 6.5 thinking it might just be an
issue with 6.4 but both failed at the same point. There doesn't appear
to be anybody else who encounter the same problem on a quick google.

Is this considered a bug with anaconda or is there some kind of
workaround such as forcing the system to mount /dev/sdb as cdrom
despite already being mounted/busy?
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[CentOS] Problem installing Centos 6.4/6.5 from USB stick seen as HDD by BIOS

[Emmanuel Noobadmin]

I'm trying to install C6.5 on a USB stick (created using Fedora
LiveUSB Creator).

The problem is the machine using an Intel ITX board sets the USB stick
as a HDD instead of a CDROM. During install, the DVD couldn't find the
installer automatically and I must choose the HDD option for it to
proceed to network/timezone/storage setup.

After the storage partitioning, it will throw an error that it is
unable to read package metadata. Although there is an option to edit
the repo information, there isn't an option to specify a hard disk.

Switching to console, attempts to mount /dev/sdb as /dev/cdrom or
/mnt/sr0 met with failure because the USB drive is in use.

Previously I used 6.4 and downloaded 6.5 thinking it might just be an
issue with 6.4 but both failed at the same point. There doesn't appear
to be anybody else who encounter the same problem on a quick google.

Is this considered a bug with anaconda or is there some kind of
workaround such as forcing the system to mount /dev/sdb as cdrom
despite already being mounted/busy?
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Re: [CentOS] hard drive question - WD red

[Emmanuel Noobadmin]

On 4/25/13, m.r...@5-cent.us m.r...@5-cent.us wrote:
 Oh, good, someone actually running Reds. How long have you had them, and
 have you had any issues? I'm not actually worried about RAID - we have a
 very few servers with RAID 1, and I think they're all software RAID. The
 big RAIDs, we bought the boxes with drives. We'd be using them for
 servers, and backups.

Sadly I don't think we have enough of them or long enough to provide
any really useful experience. Our servers are generally lightweight
systems meant to support custom apps so no hardware raid, all md RAID
1 with a pair of WD Reds on Supermicro X9SCM-F boards. 3 of them and
the oldest is only about 2 months old, no problems so far.
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Re: [CentOS] hard drive question - WD red

[Emmanuel Noobadmin]

On 4/23/13, Dan Young danielmyo...@gmail.com wrote:
 I ran across some forum posts indicating they are unlikely to work in
 arrays of greater than five disks. This is alluded to in the spec
 sheet as well.

I was concerned since we've been using Reds in our newer servers.

 http://www.avsforum.com/t/1454542/issue-with-wd-red-drives

However, the conclusion of that thread seems to put that particular
issue firmly on an odd incompatibility with the Asrock motherboard
used and the WD Red drives. One of the posters pointed out he has 12
Reds on a single Adaptec.

Somebody suggests possibly an issue with 6 drives being spread over 2
different controllers. I couldn't help wonder if it's just a Windows
driver thing.
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Re: [CentOS] Completely automatic yum updating on Centos 6

[Emmanuel Noobadmin]

On 10/26/12, Sorin Srbu sorin.s...@orgfarm.uu.se wrote:
 -Original Message-
 From: centos-boun...@centos.org [mailto:centos-boun...@centos.org] On Behalf

 Of Frank Cox
 Sent: den 26 oktober 2012 00:19
 To: centos@centos.org
 Subject: Re: [CentOS] Completely automatic yum updating on Centos 6

So if I plan to log into it remotely, I'll have to have it report its
 current
address to me on occasion.

Which probably wouldn't be a bad thing, anyway.

 How would one do that?

 Using an applet from eg Noip.com or something bashish that mails you the
 info?

Personally, for systems on dynamic IPs that I need to be able to log
into, I have cronjobs that just hit a specific web page on one of my
domains and a simple script records the IP.
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[CentOS] Removing/disabling console-kit-daemon

[Emmanuel Noobadmin]

I was trying to optimize a minimum memory VM and realized that this
process was taking up over 560M of virt memory. On googling, it seems
to be a known issue and doesn't seem to be needed except for graphical
desktop. Although virt memory isn't actual memory usage, the daemon is
still taking up almost 4MB of limited memory, which on a VM with only
384MB feels relatively significant to me.

Earlier in May, there was also a mailing list thread that indicates
removing console-kit-daemon requires getting rid of hal as well.

Is it safe to remove both console-kit and hal for headless
console-only web application VMs that also needs mdadm?
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Re: [CentOS-virt] RAID: by host or within KVM?

[Emmanuel Noobadmin]

On 8/10/12, Kanwar Ranbir Sandhu m3fr...@thesandhufamily.ca wrote:
 1. Let the KVM host manage the drives (i.e. RAID with LVM on top) and just
 assign the single volume to OMV. OMV will see it as one HD.
 2. Assign the individual drives to the OMV KVM, and let OMV manage the
 RAID creation, management, etc.

I usually go with #1 now because it makes the VM simpler and allows
add further VM easily.

 I'm not sure which one will perform better. My hunch is if the RAID
 management is left at the host level, I'll see better overall performance.
 Performance isn't exactly my number one goal here, but I don't want to
 kill
 it completely either by going the wrong way.

 On the other hand, if I let OMV do the RAID management for the media
 storage disks, I'll gain future flexibility because it'll be much easier
 to move OMV to bare metal.

You could probably plan for this by setting things up in advanced to
make it easier to move in the future.

Right now, for want of a better/simpler solution, I'm setting up
degraded mdadm raid 1 within the VM. The idea being that anytime I
want to move the VM to bare metal or another host, I could just add a
drive (or map one), let it sync, then shut it down, shift the drive
and theoretically  boot it up on the new machine.
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Re: [CentOS] IPv6 on Centos 6

[Emmanuel Noobadmin]

On 8/11/12, Alan Batie a...@peak.org wrote:
 We've been running ipv6 for a year or so now, but some of our newer
 instances (all on an ESX cluster) are not working.  It looks like it's
 all of our Centos 6 instances.  I'm hoping someone can point me in the
 right direction...

 centos666.peak.org [27] # cat ifcfg-eth0
 DEVICE=eth0
 NM_CONTROLLED=no
 ONBOOT=yes
 TYPE=Ethernet
 BOOTPROTO=none
 IPADDR=207.55.16.66
 PREFIX=22
 GATEWAY=207.55.16.1

Not sure if this is related/relevant but I remember reading this bug
about problems if PREFIX is used instead of NETMASK.

http://bugs.centos.org/view.php?id=5391
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Re: [CentOS] Urgent help on replacing /var

[Emmanuel Noobadmin]

On 8/3/12, Karanbir Singh mail-li...@karan.org wrote:
 On 08/03/2012 11:52 AM, Emmanuel Noobadmin wrote:
 I'll probably have to slowly hunt down the relevant selinux context
 one by one when nobody's screaming about the server being down.

 Would restorecon not help get this bootrapped ? and then with selinux in
 permissive mode, watch the audit log like a hawk.

fixfiles/restorecon managed to get init 5 past syslogger but it got
stuck still at NFS statd which locks up the entire server.

But with setenforce to permissive, the system appears to work fine and
yes I would be doing that watch the audit log thing during the next
scheduled down time.
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Re: [CentOS] Urgent help on replacing /var

[Emmanuel Noobadmin]

On 8/3/12, Lamar Owen lo...@pari.edu wrote:
 On Friday, August 03, 2012 06:24:46 AM Emmanuel Noobadmin wrote:
 In a moment of epic stupidity, having ran out of space on the root
 partition of a server due to /var chewing up the space, I added a
 separate drive for the purpose of mounting it as /var
 ...

 This sort of things pops up from time to time from a thread back in
 April.

Lesson learnt, never try to fix things I'm not familiar with when
feeling pressured by relentless error messages, especially if nobody
else is complaining yet.

 rpm -qa | while read line; do echo $line  rpm --setperms $line; done


 By extension:

 rpm -qa | while read line; do echo $line  rpm --setugids $line; done

 should handle ownerships.  Then, reenable selinux in permissive mode, and
 set it to relabel on the next boot.

Thanks for this tip, I'll try it and then see if there is anything
else in audit log that needs attention.
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Re: [CentOS] Urgent help on replacing /var

[Emmanuel Noobadmin]

On 8/3/12, John R Pierce pie...@hogranch.com wrote:
 if you had any database servers like postgresql or mysql, and their data
 files were in the default locations under /var, your databases are
 undoubtably corrupted, unless you stopped the DB server(s) before doing
 this copy.

I think the fortunate thing is that everything else important on the
server was running in their own VMs with their own LVM partitions. So
luckily there doesn't seem to be anything important affected by my
stupidity, the most important I wanted saved were the LVM
configuration and VM configs which fortunately were in standalone XML
files.

I *think* I probably could had quickly reinstall a bare minimum C6 to
fix it, but after realizing my epic foolishness with replacing /var, I
didn't want to take any chances of anaconda wiping all the LVM
partitions.
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[CentOS] Urgent help on replacing /var

[Emmanuel Noobadmin]

In a moment of epic stupidity, having ran out of space on the root
partition of a server due to /var chewing up the space, I added a
separate drive for the purpose of mounting it as /var

To do so, I mounted the new drive as /var2, cp -R (in hindsight should
had rsync to preserve attributes), deleted the original /var to free
up space, edited fstab and rebooted... unsurprisingly to a fubar'd
server.

The thing is it still boots, I can get into single user mode but a
full init get stuck at starting the syslogger. What is the best way to
rescue the server now from my own stupidity and keeping all the
existing configuration and data?
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Re: [CentOS] Urgent help on replacing /var

[Emmanuel Noobadmin]

On 8/3/12, Darod Zyree darodzy...@gmail.com wrote:

 Did you rewrite the selinux policy on /var or have you tried disabling
 selinux if you haven't do so already?

Thank you so much!

Turning off selinux allowed me get the system running.
However, after running fixfiles to restore the context for /var, I
still cannot boot to init 5, with the choke point now NFS statd.

I'll probably have to slowly hunt down the relevant selinux context
one by one when nobody's screaming about the server being down.
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Re: [CentOS] How to trigger automount of USB drives in Centos6

[Emmanuel Noobadmin]

On 8/1/12, Earl Ramirez earlarami...@gmail.com wrote:

 You can use the UUID instead of the device name

I thought of doing that but that assumes the same devices are used all
the time. Otherwise, I would have to maintain a list of UUIDs to add
every time and to keep trying every time the script is run which
doesn't sound very efficient to me. Thus it seems to me like there
should be a better way to do this especially since the mechanism
already appears to exist.
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[CentOS] How to trigger automount of USB drives in Centos6

[Emmanuel Noobadmin]

In brief: Is there is anyway to trigger the same automount mechanism,
that X appears to use, on unmounted USB drives that are already
connected?

Background:
I've got a C6 server with default desktop GUI installed for the sake
of the onsite admin. There is a bash script I wrote that runs every
night checking for specific folders on any drive and dumps data into
it.

To ensure fs integrity, I do an unmount in the script when it's done
in case anybody simply yanks the drive out without doing the proper
process.

Now due to that, I would need to remount the drive when the script
runs if it wasn't unplugged and replugged to trigger the automount.

Problem is, it is not certain that the same drive will be used so I
cannot simply hard code a line that just do a mount -t ntfs-3g
/dev/sde1 /media/backup. I cannot assume it would always be say
/dev/sde1 or /dev/sdf2 as that depends on how many drives are
connected before that and how was that particular drive partitioned.

The inbuilt auto mount mechanism also appears to use different
mountpoints for different USB drives (based on drive label?) and so
the best way for me is to force all USB drives to be remounted, and
scan through the /media folder as that is where the automount mounts
the partitions.

I could try to mount all drives found in /proc/partitions but that
seems very dangerous since the list includes md partitions and array
members.

So the question is whether there is anyway to trigger the same
automount mechanism, that X appears to use, on any unmounted USB
drives?

Trying resources I found online, It doesn't seem to be autofs or
gnome-mount mechanism as neither of these are installed on the server.
Both automount and gnome-mount command not found.
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/9/12, Les Mikesell lesmikes...@gmail.com wrote:
 One thing that helps is to break it up into separate runs, at least
 per-filesystem and perhaps some of the larger subdirectories.
 Depending on the circumstances, you might be able to do an initial run
 ahead of time when speed doesn't matter so much, then just before the
 cutover shut down the services that will be changing files and
 databases and do a final rsync which will go much faster.

I did try this but the time taken is pretty similar in the main delay
is the part where rsync goes through all the files and spend a few
hours trying to figure out what needs to be the updated on the second
run after I shutdown the services. In hindsight, I might had been able
to speed up things up considerably if I had generated a file list
based on last modified time and passed it to rsync via the
exclude/include parameters.

 Also, have you looked at clonezilla and ReaR?

Yes, but due to time constraints, I figured it was safer to go with
something simpler that I didn't have to learn as I go and could be
done live without needed extra hardware on site. Plus it would be
something that works at any site I needed it without extra software
too.
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/10/12, aurfalien aurfal...@gmail.com wrote:
 I do dump/restores fir this sort of thing.

Thanks for this, I didn't know there was such a command until now!
But it looks like it should work for me since bulk of the data are
usually in /home which is a separate fs/mount usually. I can always
resize the fs after transfer so I'll give this a try the next time I
need to do a dup/migrate.
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/10/12, John R Pierce pie...@hogranch.com wrote:
 dump should not be used on mounted file systems, except / in single user.

Aha, thanks for the warning!
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Re: [CentOS] kickstart installation problem

[Emmanuel Noobadmin]

On 7/10/12, jiten jha jitenjh...@googlemail.com wrote:
 Dear Friends,

 I have centos 6.2 64 bit os in my dell server. When I try to install centos
 or scientific linux using NFS so it is not working and getting me error =
 unable to download kickstart file.
 My kickstart file configuration is :

I had a somewhat similar problem with network install although I am
not sure if the same applies to you. In my case, I had to pass
additional kernel parameters to start the network interface with the
correct IP address and netmask, otherwise, it basically didn't have
networking and so couldn't download the kickstart file.
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Re: [CentOS] kickstart installation problem

[Emmanuel Noobadmin]

On 7/10/12, jiten jha jitenjh...@googlemail.com wrote:
 can you send me the command i will try it.

If I'm not wrong, these are the relevant kernel parameters you have to
add during grub/boot time. Of course please replace the n.n.n.n and X
with the correct values

ip=n.n.n.n netmask=n.n.n.n gateway=n.n.n.n dns=n.n.n.n hostname=X ksdevice=ethX
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/11/12, Les Mikesell lesmikes...@gmail.com wrote:
 Hours?  This should happen in the time it takes to transfer a
 directory listing and read through it unless you used --ignore-times
 in the arguments.  If you have many millions of files or not enough
 RAM to hold the list I suppose it could take hours.

Not that many files definitely, more in the range of tens of
thousands. But definitely more than an hour or two with small bursts
of network traffic.

 Rear 'might' be quick and easy.  It is intended to be almost
 unattended and do everything for you.  As for extra software - it is a
 'yum install' from EPEL.   The down side is that if it doesn't work,
 it isn't very well documented to help figure out how to fix it.I'd
 still recommend looking at it as a backup/restore solution with an
 option to clone.  With a minimum amount of fiddling you can get it to
 generate a boot iso image that will re-create the source filesystem
 layout and bring up the network.  Then, if you didn't want to let it
 handle the backup/restore part you could manually rsync to it from the
 live system.

I'll look into it when I need to do this again. It just isn't
something I expect to do with any regularity and unfortunately server
admin isn't what directly goes into my salary so it has to take a
second priority.
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/9/12, Micky mickylmar...@gmail.com wrote:
 The best and traditional way that has been there for decades is an rsync
 and then reinstallation of boot-loader.
 It works always if you know how it's done.

The problem I found with rsync is that it is very slow when there are
a lot of small files. Any idea how this can be improved on or is that
a fundamental limit?
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 7/9/12, John R Pierce pie...@hogranch.com wrote:
 On 07/08/12 7:14 PM, Joseph Spenner wrote:
 What is running on the server?  You might be able to get away with a dd,
 to build a duplicate disk.  This disk can be directly attached or on
 another server tunneled through ssh.

 or setup a drbd replica, wait for it to replicate, then stop the
 replication.

That requires drbd to be setup in advance doesn't it? I was trying
this approach then ran into that wall. And given the amount of work
required to get drbd working on a new setup, it seemed easier to use
mdraid to do the same thing.
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Re: [CentOS] How to handel smtp to public servers - done

[Emmanuel Noobadmin]

On 6/27/12, Götz Reinicke goetz.reini...@filmakademie.de wrote:
 Long story short: I advised the use of port 587 two hours ago.

 FYI since than I had 169 outgoing connections to port 20 and 1 to 587. :)

Seriously, just force them. I got so tired of one particular app/mail
server that keep getting blacklisted because of lazy client admin and
users, I sent them a notice that for emergency security reasons,
emails will only be accepted on port 587. Gave them one hour, then
closed 25.

Understandably people screamed for about another hour or so but all of
them ended up on 587 by the end of the day ;)
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Re: [CentOS] RAID?

[Emmanuel Noobadmin]

On 6/25/12, Warren Young war...@etr-usa.com wrote:
 Then there's the LVM option, but I can't immediately come up with a
 one-liner that tells you whether a given LVM disk set is equivalent to
 software RAID.

LVM has a mirroring option but from, possibly outdated, reading a
couple of years back, it is not as smart as md raid when it comes to
using both disks to speed up reading and will only read from one disk.
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Re: [CentOS] Centos 6 / Kickstart Using degraded mdadm RAID1

[Emmanuel Noobadmin]

On 6/10/12, Stephen Harris li...@spuddy.org wrote:
 On Sun, Jun 10, 2012 at 10:09:28PM +0800, Emmanuel Noobadmin wrote:
 #raid / --fstype=ext4 --level=1 --device=md0 raid.253001 raid.253065

 Maybe try
   raid / --fstype=ext4 --level=1 --device=md0 --useexisting
 Or
   raid / --fstype=ext4 --device=md0 --useexisting

 is I can't figure how to kickstart to the point where the mds arrays
 are created successfully.

 The command works in shell but somehow in the kickstart process, the
 created array disappears after ananconda does the Examining storage
 device thing.

 Why don't you post the necessary fragments of your ks.cfg file and the
 relevant log messages?  At least that way anyone following along won't
 re-tread your failed paths :-)

Thanks again for your suggestion, I finally got a chance to try it and
wondered why I didn't see the --useexisting option before.

However, now Anaconda complains about partitions required. Fortunately
with that additional information, it seems that this is a bug so I
don't have to keep banging my head on it.

https://bugzilla.redhat.com/show_bug.cgi?id=741728
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

On 6/14/12, Smithies, Russell russell.smith...@agresearch.co.nz wrote:
 How about using one of the backup tools to image the server?
 We use Symantec System Recovery and image all the disks. We then have the
 option of restoring to different hardware (physical or virtual) which works
 very well.
 There's a 60-day evaluation period.
 http://www.symantec.com/products/trialware.jsp?pcid=pcat_business_contpvid=1602_1

Not an option for me unfortunately, the only Windows systems on
location are at best Win7 Home Premium and SSR requires a Win Server
OS according to their page.
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Re: [CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

I'm using KVM so didn't have the tool.

While Les' suggestion looked like it was going to be pretty useful for
a variety of backup/restore situations, I didn't know if I had the
time to go through the docs and get things working in time.

So in the end I went with the repeated rSync method Scott mentioned.
The advantage is, I also went and made the new system C6 first, then
rsync the necessary data files instead of leaving it still on C5.

Thankfully nothing broke, well, except SSL certs for some reason but
that was easily fixed once people started complaining.



On 6/13/12, Tris Hoar trish...@bgfl.org wrote:

 On 08/06/2012 17:33, Emmanuel Noobadmin wrote:
 I've got a CentOS 5 server that I want to migrate over into a
 virtualized instance.
 The problem is I need to minimize downtime so was trying to figure out
 a way to live clone the original.

 Initially, I thought I could do this via exporting an iSCSI target
 from the virtual host, create a MD raid 1 array on the C5 server, wait
 for it to sync, then shutdown the physical server and switch to the
 virtual one.

 But after getting iSCSI working... I realize I could not create a md
 device on a mounted disk. Unfortunately this old C5 wasn't setup with
 md raid 1 originally so I can't just add a the iSCSI target as an
 additional member for a triplicate.

 So I remembered DRBD was supposed to be used for replication.

 But after getting things set up, running the drbd-admin create-md
 command gave me this scary warning it will destroy data on the disk.
 Apparently because drbd writes meta data to the drive. So that appears
 to be a no go too.

 Am I missing something glaringly obvious here, or is the only way I'm
 going be able to migrate is to shutdown the C5 server for a few hours
 while duping the old drives? Would greatly appreciate any pointers how
 best to do this.


 You don't say what virtualisation platform you are using is, but if it's
 VMware, then you can use VMware converter to do the migration. This can,
 if you want, clone the physical computer into VMware, shut down the
 physical computer and bring up the new virtual instance. All whilst the
 physical remained up. I've used it for a few Linux boxes, where I've
 wanted a quick dev version of an existing server and its been fine.

 I guess, you could try pulling it into an ESXi host, and then exporting
 that in a format whatever virtualisation program it is you use supports...

 Regards,

 Tris

 *
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[CentOS-virt] 100% load on core after physically removing USB storage from host

[Emmanuel Noobadmin]

I encountered a problem after removing a USB flash drive using virtual
machine manager, I
notice that the core assigned to the VM guest goes up to 100% load.
Within the guest itself, there is no significant activity.

This also prompted me to look at the other physical machine from which
I used the USB flash drive to transfer files. And it was also
exhibiting the same problem.

Installed versions are
qemu-kvm-0.12.1.2-2.209.el6_2.5.x86_64
on CentOS 6.2, 2.6.32-220.17.1.el6.x86_64 (Intel C204 PCH)

There are no error messages in the log files and things seem to be
working except for the fully loaded core.

After some testing, the only steps needed are
1. VMM add physical host usb device - select storage to guest
2. VMM remove hardware
3. Physically remove the USB storage from the host, thread/core
assigned to guest goes 100%

Repeating the same steps without restarting the guest causes cpu
utilization to drop back to normal for about a second or so before
going back up again.

Problem goes away if I restart the guest. There don't seem to be anything
related on RHEL bugtrack except one related to hotplug/unplugging a
USB controller more
than 1000 times.

Is this is a bug or there is actually something else I am supposed to
do before removing a physical device from a guest?

Also is there anyway I get the core/thread back to normal without
restarting the guest?
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[CentOS] Centos 6 / Kickstart Using degraded mdadm RAID1

[Emmanuel Noobadmin]

I'm trying to install a bunch of C6 involving initially degraded mdadm RAID 1

Anaconda refuses to let me create a RAID 1 array with only one member.

Based on some reading, it seems that I should be able to use kickstart
with the PRE scripts to do this. However, after trying for a couple of
hours, it doesn't seem that anaconda will allow it, it just boots the
created arrays. At best I end up with a list of softraid partitions
instead.

Am I trying the impossible or has anybody done this before and can
point to a resource how on this can be done?
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Re: [CentOS] Centos 6 / Kickstart Using degraded mdadm RAID1

[Emmanuel Noobadmin]

On 6/10/12, Stephen Harris li...@spuddy.org wrote:
 Can you do what you want via the GUI installer?  Potentially by dropping
 into a shell to do parts of it (eg build the raid array degreaded,
 then use the GUI to install onto that).  If so, manually do an install
 and then look at /root/anaconda-ks.cfg to see what file that built out.
 It might provide the hints you need.

I did do that initially to check it was doable. Unfortunately the
anaconda-ks.cfg in that config gave very little clue what was done,
there are just 4 relevant lines which look like this
#raid / --fstype=ext4 --level=1 --device=md0 raid.253001 raid.253065

Nothing usual, and make sense since I created the md arrays and
ananconda simply used them without assembling them itself. The problem
is I can't figure how to kickstart to the point where the mds arrays
are created successfully.

The command works in shell but somehow in the kickstart process, the
created array disappears after ananconda does the Examining storage
device thing.
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Re: [CentOS] Centos 6 / Kickstart Using degraded mdadm RAID1

[Emmanuel Noobadmin]

On 6/10/12, Stephen Harris li...@spuddy.org wrote:
 Maybe try
   raid / --fstype=ext4 --level=1 --device=md0 --useexisting
 Or
   raid / --fstype=ext4 --device=md0 --useexisting
 Why don't you post the necessary fragments of your ks.cfg file and the
 relevant log messages?  At least that way anyone following along won't
 re-tread your failed paths :-)

Thanks for the suggestion, I'll try it on a VM and post the cfg file
after I'm done fighting the current fire! :)
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[CentOS] Best way to duplicate a live Centos 5 server?

[Emmanuel Noobadmin]

I've got a CentOS 5 server that I want to migrate over into a
virtualized instance.
The problem is I need to minimize downtime so was trying to figure out
a way to live clone the original.

Initially, I thought I could do this via exporting an iSCSI target
from the virtual host, create a MD raid 1 array on the C5 server, wait
for it to sync, then shutdown the physical server and switch to the
virtual one.

But after getting iSCSI working... I realize I could not create a md
device on a mounted disk. Unfortunately this old C5 wasn't setup with
md raid 1 originally so I can't just add a the iSCSI target as an
additional member for a triplicate.

So I remembered DRBD was supposed to be used for replication.

But after getting things set up, running the drbd-admin create-md
command gave me this scary warning it will destroy data on the disk.
Apparently because drbd writes meta data to the drive. So that appears
to be a no go too.

Am I missing something glaringly obvious here, or is the only way I'm
going be able to migrate is to shutdown the C5 server for a few hours
while duping the old drives? Would greatly appreciate any pointers how
best to do this.
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Re: [CentOS] CentOS, XFS, VirtualBox - can they just get along?

[Emmanuel Noobadmin]

On 4/26/12, Boris Epstein borepst...@gmail.com wrote:
 Hello all,

 I am running VirtualBox 4.1 on CentOS 6 and I got this warning that putting
 your VM's into an XFS filesystem is risky. I have also heard some rumors on
 the net to this effect. Does anyone know in more detail what's behind those
 rumors?

I came across the same warnings while looking up on using XFS as the
fs on storage nodes. IIRC it has to do with caching and flushing to
disk.

From what I understood:

VM caches writes before sending it to the virtual disk.
Host's XFS does delay logging to address performance issue before
sending it to the HDD
HDD caches writes for performance and may not respect commands that
demand it turn off caching and flush writes.

If a power cut occurs, in the absence of a BBU HBA, it seems that it
is indeterminable if the last few writes had been committed and in
what sequence and usually means a corrupted VM.
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Re: [CentOS] SSD for boot drive and OS

[Emmanuel Noobadmin]

On 4/15/12, Frank Cox thea...@melvilletheatre.com wrote:
 I'm just thinking... I wonder if it would be possible to somehow replicate
 the
 OS on both the SSD and the hard drive, such that you could just change the
 boot
 device in the bios to point to one or the other.  Which wouldn't exactly be
 a
 raid (with the overhead that entails) but just a change of boot device as
 required.

This is an interesting idea, especially with using a small cheap SSD
to boost boot speed.

Don't see any reason why it cannot be achieved simply by doing the
same thing of using mdraid RAID 1 with partitions and using the
write-mostly on the HDD partitions.
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/10/12, m.r...@5-cent.us m.r...@5-cent.us wrote:
 Two questions: a) are you sure that the USB key is /dev/sda,
Yes, I've verified this before and again after you asked that it is
seen as /dev/sda, at least through the installation DVD. fdisk also
does not find a sdb/c/d if I try that.

and b) does your system offer a boot menu, or only go into setup to tell it to 
boot
 off the USB key?

Both, I can set the boot sequence in BIOS, which is currently to boot
USB first. And I can also hit F10 to choose.

 Oh, and in fdisk, is the partition flagged bootable?
Yes, definitely :D
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/10/12, Phil Schaffner philip.r.schaff...@nasa.gov wrote:
 Have you tried the grub find command?
 find /grub/stage1
 find /boot/grub/stage1
 etc.

 http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB

I've tried that now but it could not find any of the files be it
stage1, grub.conf or menu.lst, also tried both /grub and /boot/grub
variants.

The interesting thing is that if I leave the DVD in the DVDROM drive,
grub will find it as hd111 with the tab button. So the tab
functionality is actually working. Just that as far as grub is
concerned, the flash drive it just loaded from just seem to be
undetectable.
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On a random hunch or sheer desperation, I inserted an old brandless
1GB USB thumbdrive, installed and it booted.

Thinking that the Sandisk Ultra Backup 16GB was incompatible with
CentOS/grub for some unknown reason. I switched to a brandless 16GB,
installed the same way and it failed at grub prompt again.

Now it is starting to look as if either the newer drives have
something on them that prevents booting. Or it's the total size of the
drive, regardless of the partition size. I say this because in every
case I used a single 1GB ext4 / partition for testing, to reduce the
mkfs time.

Since now I have a bootable drive, I started to compare them with
fdisk to see if there was any difference.

Bootable
255 heads, 63 sectors/track, 124 cylinders, start sector 63
With a warning that
Partition 1 has different physical/logical endings:
phys=(123, 254, 63) logical=(124, 140, 16)

Unbootable 16GB Sandisk Ultra Backup
54 heads, 48 sectors/track, 12158 cylinders, start sector 2048

Unbootable 8GB Sandisk Blade
20 heads, 4 sectors/track, 195417 cylinders, start sector 2048

Unbootable 16GB Unbranded
171 heads, 40 sectors/track, 4634 cylinders, start sector 2048

It seems that the common issue is starting at sector 2048 so I fdisk
the 16GB Sandisk to manually create a 1GB partition started at sector
63. Using this, I installed and was able to boot successfully.

To verify, I use the same 16GB disk to install again, deleting the
partition in anaconda and creating a new 1GB partition, ctrl-alt-f2
and fdisk confirms it was again at sector 2048.

As a side note, for some reason, drive geometry changed for the 16GB
after a reinsert to varying values such as
6 heads, 33 sectors/track, 159164 cylinders
16 heads, 32 sectors/track, 61551 cylinders

Not sure if this had any significance to why anaconda decides to fdisk
the drive starting from sector 2048.

My only guess is that it considers anything bigger than 4GB as a
normal HDD drive and does this for hard disk alignment issue? But if
grub could boot normally from such a HDD, why would it choke on a USB
flash drive?

Should I report this as a bug with anaconda or ?
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/13/12, m.r...@5-cent.us m.r...@5-cent.us wrote:

 Wonder if it's trying to beat the rush - after weeks of googling, a few
 weeks ago, I finally found that if I formatted my 3TB drives on a 4k
 boundry, instead of a 512byte boundry, writes were literally about four
 times faster, because that's the physical sector on the drives.

 It may be trying to do the same, to take care of this invisibly.

That is what I think the 2K first sector is supposed to do, align the
physical sector be it a 512 or 4K drive. But unfortunately, the check
for is this a 4K HDD appears to be naive.
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

In trying to solve this problem, I came across these two articles
regarding GRUB and USB booting.

http://vlinux-freak.blogspot.com/2011/01/how-to-create-grub-boot-floppy-usb.html
http://bootloader.wikidot.com/linux:boot:usb-grub

The floppy drive issue appears to be the situation as booting the
rescue environment from a USB DVD does show up as /dev/fd0.

However, the solutions in those articles did not work. In the first,
the GRUB command/options are different, although changing the option
from boot-directory to root-directory appear to work, there was no
option to force floppy drive.

In the second, the python script thinks the grub install has already
been patched for floppy boot so couldn't do anything.

I've also tried editing menu.lst to use (fd0) but also didn't work.
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/10/12, Phil Schaffner philip.r.schaff...@nasa.gov wrote:

 Have you tried the grub find command?
 find /grub/stage1
 find /boot/grub/stage1
 etc.

 http://wiki.centos.org/TipsAndTricks/TroubleshootGRUB

I'm deeply embarrassed and stunned by why I did not stumble across
that googling or how I could miss seeing the command in grub shell and
doc. I'll try this the next time I get to that machine again.

Thank you very much!
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/10/12, Patrick DERWAEL patr...@derwael.be wrote:
 Emmanuel,
 I used a totally different approach by using VMware: the trick is to
 install on a physical device which is the USB drive.
 When the installation requests a reboot, simply boot on your USB and off
 you go!

That is pretty much what I did. Boot DVD 1 with a USB DVD drive,
install to /dev/sda which is the USB flash drive. When the
installation requests a reboot, shutdown, remove as well as leave the
DVD drive around and reboot... and only grub prompt or Error 21.

Maybe there's a minor but critical step I'm missing so I'll appreciate
it if you could outline in greater details how you did it.

I've tried installing grub to both MBR i.e. /dev/sda as well as first
partition /dev/sda1 but neither works.
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/5/12, Lamar Owen lo...@pari.edu wrote:
 The grub order and names and the linux kernel/udev order and names should
 not be assumed to have any correlation of any kind, since they are
 discovered differently.

Yes, that is what I understand from the grub manual. However, from
that I also understand and expect the first and only device grub could
find would be hd0

 If you can boot a USB live media on this box, you could bring up a grub
 shell and see how grub sees the disks from that (at a root prompt, type
 'grub' and you'll be greeted with the grub shell, and then you can do
 detection or whatever from that).  This also works in the rescue environment
 given by the install media; you do want to do a 'chroot /mnt/sysimage' in
 that shell before entering the grub shell, though.

I've done this previously from the rescue environment but got no
closer to resolving this.

I've tried it again with a default install of CentOS 6.2, using
default drive layout and all.
On first boot, I get the grub shell but I have not been able to find
any command that would list valid devices grub can find, apart from
the tab button.

Rebooting into the rescue environment, chrooting into the drive,
grub-install generates the map to hd(0) which was expected. Runing
grub shell and trying root (hd0) also works.

However, rebooting after updating the grub device map always results
in Booting from local disk... Error 21 which indicates grub couldn't
find the drive specified.

Any ideas how I can probe/list devices within grub shell? I've done
the stupid method of root(hd0,x) all the way up to root(hd8,3) without
luck.
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[CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

I'm trying to setup a very small system intended for doing
monitoring/logging. It's done on an Intel Atoms in a small box and the
idea was to simply run it off a pair of USB flash drives in software
RAID 1.

Now the problem is that while the 6.2 DVD installer could go through
the entire install process, grub will load then just stop at the
prompt. The system will work if I use a SATA hard disk so motherboard
compatibility is not an issue.

Attempting the various methods to re-install grub (via rescue mode) or
using the grub prompt to setup the disk does not work either. grub
just does not seem to be able to find the USB drives. e.g. commands
like root (hd0,0) just says device not found. This is despite grub
having just loaded from it and despite that grub-install in rescue
mode does not report any error.

Same problem even if I just go with one USB drive in a plain vanilla ext3 setup.

It seems that some sites are saying that EL variants just don't seem
to be adaptable to installing and running off USB drives. Is this
really the case and that I should be looking at using another
distribution or am I just missing some crucial steps in the process?
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Re: [CentOS] Installing CentOS 6.2 *TO* a USB drive, not installing from USB.

[Emmanuel Noobadmin]

On 4/4/12, Karanbir Singh mail-li...@karan.org wrote:
 On 04/04/2012 11:46 AM, Emmanuel Noobadmin wrote:
 just does not seem to be able to find the USB drives. e.g. commands
 like root (hd0,0) just says device not found. This is despite grub

 hd0,0 represents the bios device id, are you sure thats what your bios
 thinks the usb disk is at ?

I can't be sure which is part of the problem. Because when I read the
grub documentation, it said that hitting tab at the prompt after
typing the command will produce a list of possible devices/drives.
However, in my case, nothing happens which seemingly implies grub
could not find any device.

I also did try manually doing (hd0,1), (hd1,0) but none of it seemed
to be a findable device. For what it's worth, the installer did see
them as sda and sdb. I also disabled the onboard SATA controller
during my attempts in order to eliminate it from showing up as a
possible device, since grub doc says the (hdx,x) number usually
matches the order in which the devices were discovered.
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Re: [CentOS] CentOS 5.7 Ethernet bonding - order of enslavement matters?

[Emmanuel Noobadmin]

On 10/19/11, whitivery co55-s...@dea.spamcon.org wrote:
 Thank you for the reply, but I don't think that this is the issue.
 Otherwise bonding failover wouldn't work at all.  When enslaved in order
 eth1 eth0, bonding and link detection work properly - with eth0 set as
 primary, I pull the eth0 cable, it switches to eth1; plug eth0 back in, it
 switches back to it; pull the eth1 cable, it knows there's no fallback.
 So the link detection seems fine.

Ok, that does eliminate eth0 link detection as the source of the
problem. I think you might have to ask on another mailing list. It
seems like it should be the kernel list but not 100% certain.
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Re: [CentOS] CentOS 5.7 Ethernet bonding - order of enslavement matters?

[Emmanuel Noobadmin]

On 10/13/11, whitivery co55-s...@dea.spamcon.org wrote:
Eth0 is the onboard device, using an updated VIA Velocity driver
(velocityget 1.42 instead of default via-velocity):

05:00.0 Ethernet controller: VIA Technologies, Inc. VT6120/VT6121/VT6122
Gigabit Ethernet Adapter (rev 82)

Eth1 is a Linksys (Cisco) USB300M USB-Ethernet dongle, using asix
driver:

Have you tried adding another Ethernet adapter? This is because I was
reading the bonding doc and towards the end there was this part

As discussed in the options section, above, some drivers do
not support the netif_carrier_on/_off link state tracking system.
With use_carrier enabled, bonding will always see these links as up,
regardless of their actual state.

So it might a driver issue, i.e. the VIA driver is not reporting the
link down correctly.
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Re: [CentOS] CentOS 6 is a bear

[Emmanuel Noobadmin]

On 10/8/11, Bob Hoffman b...@bobhoffman.com wrote:
 Gotta say, centos has been tough to install and get working.

 The anaconda installer makes large drive setups horridly tedious
 (especially if reinstalling a lot).

I usually try to speed reinstall up by using small / and not
reformating /home. Not sure if it would be useful in your case.

That said, I haven't had all the troubles you have on my sole C6 test
server, before and after installing the desktop package.

 Any attempt to disable or make selinux permissive results in a dead
 machine, unable to ever boot again (left one up for 12 hours, never came
 back up, thought it was relabeling, but no message.)

This is rather odd, I only ever had problems with selinux set to
enforcing. It should be relabelling if you had disabled it. Could
there be some problem with your server hardware that's throwing you
off with all these spurious problems?

 I have never, not once, been able to connect to the net in the command
 line setups...I know how to configure eths, network, dns, etc...not
 once, not even dhcp..config eth0 up, etc.. Gnome has not a single issue
 with the same exact file setups.. Many command line setups would not
 even see the eth devices, something about modprobe this or that not
 installed.wth?

Do you happen to be using an Intel NIC ? Several of us were having
problems until we switched to using the kmod drivers from elrepo.
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Re: [CentOS] Choosing a CentOS version

[Emmanuel Noobadmin]

On 10/4/11, m.r...@5-cent.us m.r...@5-cent.us wrote:
 Note that the above is true of every single o/s: for example, I think
 Windows XP is approaching EoL, while Internet Exploder 6 is *past* that
 (and there was much rejoicing).

IIRC WinXP is already EoL'd for general end users but still a couple
of years for those on extended commercial support.
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Re: [CentOS] Hard I/O lockup with EL6

[Emmanuel Noobadmin]

On 9/27/11, Benjamin Smith li...@benjamindsmith.com wrote:
 I wish you the best of luck!

Fortunately (or unfortunately depending on how one looks at it), mine
appears to be just bad sectors developing on one of the  newest
drive I added to the machine as part of a mdadm RAID 1 array.

After I rebooted the server and after some period of non-activity
apart from the raid resync, I came back to see the console scrolling
with error messages and an email warning in my inbox that a device has
failed.

smartctl quick test aborted with a read error but WD's diag reports no
problem on a quick test so I'm putting it through the full media scan
to be sure.

Hopefully it is indeed just bad sectors but I'm skeptical at this
point because in the original situation, there was no warning email
from mdadm and there was nothing logged when I checked.
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Re: [CentOS] Hard I/O lockup with EL6

[Emmanuel Noobadmin]

On 9/27/11, Benjamin Smith li...@benjamindsmith.com wrote:
 When booting a non-working system, it boots straight up to the boot prompt
 (runlevel 3) without issue, and everything works fine. When the machine sits
 idle for a period of time (ranging from 15 minutes or so and up) the HDD
 becomes unreadable/unwritable and the system is useless for any purpose and
 must be hard restarted with a full power cycle - it won't even shut down.

I'm thinking I might have a similar problem with my test install of
EL6. Initially I had dismissed it as a one-off but it has apparently
locked up again. I'll be visiting it physically later and maybe have
more information to share. However, it is also a 3400-series Xeon, the
rest of the hardware are all cheaper hardware.

What drives are you using in these servers?
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Re: [CentOS] RTL8111/8168B always 100mbps

[Emmanuel Noobadmin]

On 9/27/11, Muhammad Panji sumodi...@gmail.com wrote:
 Dear All,
 I have an onboard Realtek RTL8111/8168B NIC. from lspci -vv :

 02:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
 RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 02)

 It is detected, but why the speed is always 100Mbps, already change
 cable but still no luck. I use ethtool and from the output it seems
 that system know that this NIC support gigabit speed :

What network switch is this connected to? Does it work if you disable
auto-negotiation and force the link speed to 1Gbps?
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Re: [CentOS-virt] Network and IP's

[Emmanuel Noobadmin]

On 9/22/11, Thomas Rønshof t...@kyborg.dk wrote:
 Hi,

 When playing with Cent OS 5.x Virtualization, I could have a host with
 IP:192.168.10.40 and the guests with IP's: 192.168.10.41,
 192.168.10.42... an so on.

 But now after installing Cent OS 6.0 as a host, I can't figure out how
 to make my guest get the same IP's.

 My host is still 192.168.10.40, but the 1. guest i make, get an IP of
 192.168.122.x !

 I can see something in virtual-manager concerning virtual-networks. It
 looks new compared to COS 5.x.

 Is it not possible ?

I'm probably missing something here but doesn't editing ifcfg-ethX in
the guest give them the required IP or is virt-manager overriding
those settings?
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Re: [CentOS] Problems with Intel Ethernet and module e1000e

[Emmanuel Noobadmin]

On 9/23/11, Volker Poplawski vol...@openbios.org wrote:
 Hi all,

 I'm facing a serious problem with the e100e kernel module for Intel
 82574L gigabit nics on Centos 6.

 The device eth0 suddenly stops working i.e. no more networking. When I
 do ifconfig from console I get
.
.
.
 Bringing down the interface with ifconfig eth0 down and then ifconfig
 eth0 up does not help. A reboot gets the interface back to normal. The
 problem returns after some minutes, hours or a day.

I had the same problem with an Intel Gigabit NIC and the e1000 module
just last week on a fresh CentOS 6.0 install. Network will die for no
explicable reason and fixable only by reboot.

Problem was solved by following one of the threads in the CentOS forum
IIRC, using the elrepo kmod drivers.
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Re: [CentOS] This doesn't make sense

[Emmanuel Noobadmin]

On 9/24/11, Johnny Hughes joh...@centos.org wrote:
 I can tell you that we are building 6.x stuff for QA now and have been
 for several weeks.

I'm not personally unhappy with the devs over the situation since I
pretty much didn't plan on any critical C6 installations until 6.1
comes out. So with just one testing/internal-only C6 server, these
security issues are largely not a non-concern for me.

So just voicing my 2 bits worth...

As with the 6.0 release, the problem I see is a lack of communication
rather than the actual speed of release. The qaweb was a nice step
forward in the weeks before 6.0, then right after the 6.0 release, it
became for all practical purposes dead.

With the 6.0, I think most of us could understand and accept that it's
an entirely new environment. But why is 6.1 taking so much longer,
especially the CR which was mentioned to become available within days?
More so since it appears that most of the 6.1 packages are built and
ready.

It probably would had been OK if there was a follow up that simply
stated there were unexpected issues and the CR could not be roll out
anytime soon. Otherwise there are some that likely took the dev's word
for it that at least critical security updates would be available
through CR and so 6.0 is OK to go.

In summary: please make use of the existing QAWeb and Communicate with
the Community.
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Re: [CentOS] This doesn't make sense

[Emmanuel Noobadmin]

On 9/24/11, Lamar Owen lo...@pari.edu wrote:
 I don't think you understand.  The process is iterative; if QA fails it's
 all the way back up to building it again.  A package may have existed three
 weeks ago in terms of being built; if that package had passed binary testing
 and QA it would have been released by now.

I think most of us already understand this part due to the discussions
during the pre 6.0 release. The whole point is about the
communication.

 As to 'fun' entering into it, you also realize these guys are volunteers,
 right?  Make a volunteer's life too hard, and that volunteer stops
 volunteering.  These volunteers *owe* the users of CentOS *nothing*.  I'm
 just glad they've done what they've done.

I appreciate what the CentOS team has done. Certainly I wouldn't had
been able to offer the typical budget-constrained clients I get, the
equivalent of RHEL they are using now. That said, just because we're
doing volunteer work, does not mean we can be totally irresponsible. I
did and still do pro bono work for certain non-profit organisations in
my country. They understand perfectly that they aren't paying a cent
and have no right to make demands. Nevertheless they do have general
timelines and decisions that have to be made based on whether certain
features are ready or not. It is my responsibility to tell them if
something comes up and I cannot expect to implement certain things
within the original estimated time. They aren't going to get pissed,
they will either change their plans or seek additional help and be
thankful that I didn't kept mum until it's too late to do anything
constructive.

Similarly, I think that's what most of the people screaming are
expecting as the bare minimum. If a build goes to QA, just post an
update. If the build fails QA, post an update, we will understand that
probably means at least 2~3 weeks of delay, no biggie, there is info,
we can make plans and decisions. Everybody's cool. For just a 3 minute
effort, the devs won't have to waste time on replies when negativity
build up spills over.
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Re: [CentOS] This doesn't make sense

[Emmanuel Noobadmin]

On 9/24/11, Johnny Hughes joh...@centos.org wrote:
 Yes, I suck at communication.  Just ask my 1st wife.

Does that mean that the whole dev team are just going to chalk it up
to poor communications, shrug and not do anything about the
communication channel, despite the existence of the qaweb and that it
probably takes less than 3 minutes each time to post something like
Latest build going for QA, 14 packages failed QA, back to respin?

Probably a lot less time wasted with those short updates than just
reading the flare up mails.
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Re: [CentOS] 6.1 Release

[Emmanuel Noobadmin]

On 9/24/11, TE Dukes tdu...@palmettoshopper.com wrote:
 OK,

 So how can we help getting CentOS 6.1 released? This is a Community
 project. I'm not a programmer, IT person but I do ask a lot of help from
 this list. What do we need to do or how can the 'average person' help? Can
 you send us some files to test? What? I'd like to help but don't know how.

Based on what I remember of past responses, the short answer is: nothing.

By the time the devs are already spinning the release, they don't have
time to get new people familiarized with the process so they are only
willing to do it during the lull period between releases.

You could start by getting familiar with development process by taking
on a specific module as a personal interest. Maybe starting from doing
a howto/wiki, then beta testing new releases for that module, moving
on to submitting patches and by the end of a couple of years you would
probably be expert enough to help take on the entire module for CentOS
7. But this of course won't help get 6.1 out the door faster.

Besides that, the average person could make the next release better
(but not faster) by testing the RHEL beta or Fedora, filing bug
reports and generally make the whole distribution better. But this
won't get CentOS out the door faster.
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Re: [CentOS] kickstart: gfx vs. txt mode

[Emmanuel Noobadmin]

On 9/24/11, Eric Sisolak haldir.j...@gmail.com wrote:
 This is usually caused by not having enough RAM.  I think for el5 you need
 either 512 or 768MB and for el6 it is more like 1GB (IIRC).

Should be 768MB for EL6 based on my recent EL6 VM installation. It
just seem rather silly that the installation requires about 3x more
memory than the 256MB required for actual operations.
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Re: [CentOS-virt] Getting guest to detect new drive without reboot

[Emmanuel Noobadmin]

On 9/20/11, Ian Forde ianfo...@gmail.com wrote:
 Partprobe

Thanks for pointing this out, although due to time pressure I did the
nasty in the end, kicked everybody off and rebooted the server. But
I'll keep this in mind the next time I need to do this again, probably
sooner than later.
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[CentOS-virt] Network traffic control/shaping of guest interfaces

[Emmanuel Noobadmin]

I've been using tc/htb for network control previously to control
bandwidth available to different services running on their own IPs on
a unvirtualized host.

Now, I have put them into their own guest VM. I would like to be able
to do something similar to ensure the more crucial service gets more
bandwidth as well as ensuring ssh always get reserved bandwidth.
However, when I try the good old tc/htb commands on the host, it fails
to do anything useful.

My script that works on the non-virtualized setup was this

TCADD=tc class add dev eth0 parent
$TCADD 1:0 classid 1:1 htb rate 1250kbps ceil 1250kbps
$TCADD 1:1 classid 1:10 htb rate 25kbps ceil 150kbps prio 0
$TCADD 1:1 classid 1:11 htb rate 100kbps ceil 300kbps prio 1
$TCADD 1:1 classid 1:12 htb rate 300kbps ceil 600kbps prio 1
$TCADD 1:1 classid 1:19 htb rate 75kbps ceil 150kbps prio 2

TFADD=tc filter add dev eth0 protocol ip parent
$TFADD 1:0 prio 0 u32 match ip dport 10022 0x flowid 1:10
$TFADD 1:0 prio 1 u32 match ip dst public ip ipaddress 1 flowid 1:11
$TFADD 1:0 prio 1 u32 match ip dst public ip address 2 flowid 1:12

I can't put the restrictions within the guest because I don't want the
individual VM admins to be able to stop the script from running.

On my new host, I have bridged networking with br0, eth0 and guests
running off vnetn.
I've tried applying tc on br0, eth0, vnetn but they don't seem to
have any effect based on a 20MB FTP test.

I've been googling for a while to find an solution but haven't hit on
anything apart from using yet another firewall/router sitting between
everything and the Internet. Is there any other solution apart from
that?
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Re: [CentOS-virt] Network traffic control/shaping of guest interfaces

[Emmanuel Noobadmin]

On 9/21/11, Nenad Opsenica ne...@panline.net wrote:
 I would convert bridged setup on host to the routed one.
 Then you will have several separate interfaces on host, each one used
 for communication with only one guest and it will be easy to attach tc
 to them.

In other words, there's no solution for bridged networking?

How would routed networking impact the guest performance? The reason I
went for bridged was that it was supposed to have the least overheads
and here 
http://www.cyberciti.biz/faq/rhel-linux-kvm-virtualization-bridged-networking-with-libvirt/
said it was required for servers with multiple network cards. Which is
the case here because I have 3 NICs, one each for Internet traffic,
networked storage and user access.

Although, admittedly on hindsight, given the number of users in the
company, it probably isn't going to be noticeable I would still like
to know what kind of impact would it cause. That is assuming routed
networking can work on the server given the NICs in it.
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Re: [CentOS-virt] Network traffic control/shaping of guest interfaces

[Emmanuel Noobadmin]

On 9/21/11, Nenad Opsenica ne...@panline.net wrote:

 You can combine bridged and routed setup - for example, use bridging for
 storage, routing for internet and user access.

 Using routed setup have one more advantage - you can use firewall on
 host to filter guests' traffic.

Thanks for the tip, I'll have to look into this during the weekends
when, almost guaranteed by virtue of noobness, I will probably kill
connectivity to the services for hours and render it useless for work
:D
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Re: [CentOS] Installation of 6.0

[Emmanuel Noobadmin]

On 9/21/11, Al Sparks data...@yahoo.com wrote:

 Some observations.

 When I installed 6.0 (base install), the installation interface did not
 guide me through a network configuration.  I do static IP addresses, not
 DHCP.

IIRC, it's in this small unobstrusive rectangular box that says Setup
Networking or something like that in the lower left corner in the
screen that ask for hostname. I'm not sure if this was the way
upstream or adjustments made by the CentOS devs, but I'm guessing that
the assumption is most people are going for DHCP-based installs so it
saves some time.

 Anyway, I wasn't able to find a configuration program like netconfig to
 help me out.  Seems like a pretty big omission.

 Any thoughts?  Am I missing something?

I think it's been mentioned that was taken out. In any case, I've been
getting used to turning off NetworkManager and editing ifcfg-xxx and
/etc/resolv. Compared to obscurities like samba and libvirt, I'll say
these are pretty doable in nano.
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[CentOS-virt] Getting guest to detect new drive without reboot

[Emmanuel Noobadmin]

I've got a CentOS 5.6 guest running on 6.0 host.

Using virsh attach-disk, I attached a new raw file as vdc
However, the guest does not detect this new disk.

In the past, I've used the following
echo 0 0 0  /sys/class/scsi_host/host#/scan

command to make a CentOS system scan for new drives.

However in the guest, there is no host in scsi_host so this isn't an option.

I can't seem to find any information on doing this any other way apart
from a reboot. Does anybody know if there is any other way?
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Re: [CentOS] Was: Re: Upgrade from 5.6 = 5.7, is, programming with style

[Emmanuel Noobadmin]

On 9/16/11, m.r...@5-cent.us m.r...@5-cent.us wrote:
 Remember, even among those who studied, a) half of them were in the bottom
 of their class, and b) too many are True Believers in the latest
 programming (not the P word!) paradigm; y'know, recursion is the answer to
 *everything*, or OO, or

Part of the problem is sometimes otherwise intelligent customers who
heard of the latest buzzword be it XML/Ruby/Web 2.0/HTML5 start
demanding that you use it for their application regardless of whether
it's relevant or if they really know what it is about . If you try to
educate them any other way, they start thinking you're outdated.

On top of that, sometimes you have to work with people who are True
Believers or Purists...
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Re: [CentOS] centos product specification

[Emmanuel Noobadmin]

On 9/17/11, Always Learning cen...@u61.u22.net wrote:
 and it is not black

   color: #464646;

While the exact optimal shade is arguable (a tad too light IMO), past
ergonomics studies indicate that extreme contrast such as #00 on
#ff is more tiring to read so can't really fault the devs on this
one.

 Anyways, most every browser has a zoom function for those who refuse to
 wear corrective lenses, often alt + and alt - ...

 Readers of material in browsers should not have to routinely alter their
 browser's display settings to compensate for poorly designed web sites.

Developers of websites should not have to alter their site design to
compensate for a minority's refusal to make full use of the tools at
their disposal. ;)

It might be better to file the bug report against the website for the
missing documentation that to harp on the design :)
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/16/11, Always Learning cen...@u61.u22.net wrote:
   C1

   c1ref
   c1customer  (code)
   c1quantity  (integers only)
   c1price (in cents)
   c1discount  (2 decimal places held as integers)
   c1catalogue (code)
   c1date  (yymmdd)
   c1order (number)
   c1comments  (text)

 then do a query:

 select c1quantity, c1price, c1discount from c1 where c1customer =
 'joebloggs' and c1date like '10%'

Isn't it bad practise to store customer reference by name? What
happens if we want to look up a customer called John Smith and there
are say a dozen of them?

I would at the very least have a separate table holding core customer
information with an auto-incremented ID so that customers with the
same name won't cause a problem. Of course, that would mean requiring
a join on the query, or at the very least two queries with one pulling
the customer ID first. Although since the base customer ID table is
usually a frequently accessed but not changed table, it's likely to be
in memory and therefore faster to issue a join, which the dbms should
handle smartly enough than to separate queries.
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/15/11, Always Learning cen...@u61.u22.net wrote:
 I have written 20+ complete systems using these and found them to be
 fast and very effective. Everyone who has seen my HTML, CSS, PHP, MySQL
 systems has been favourably impressed (me too!). MySQL is a fast
 database system. Never ever used a SQL join or view, just well designed
 databases with carefully planned tables - that is the art of good
 programming.

So how do you retrieve data that are kept in different tables? Or do
you simply replicate the same data in every single table that needs
it?

 Ajax/Jquery is someone else's parametrised programming language. It adds
 complexity and overhead to what is fundamentally a very basic task. Ajax
 etc. seem to appeal to people who are not good (or natural) programmers.
 Ajax etc. is like programming with boxing gloves on and taking several
 weeks to do it. If they want to use it, let them.

While I'd agree with you somewhat on jQuery and frameworks, AJAX isn't
the same thing. It's just a style of user interface that does make the
application more user-friendly. After all, in the hypothetical
accounting program, wouldn't typing a few letters in the invoicing
page to start displaying a list of possible customers be more
efficient than having to go to a separate search page to list and
select a customer?

 also, I'd suggest using postgresql for better data integrity, and
 anything-but-php (Python?) for better webside security.

 I have been using MySQL on Linux for about 4 years and never had a
 problem. What security issues has PHP ?

In my largely unresearched opinion, the same security issues that any
server side language might have: careless or naive programmers.
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/15/11, Always Learning cen...@u61.u22.net wrote:

 Next you'll be saying you don't use triggers and constraints either.

 Not consciously. Never heard of them.

You should take a look at constraints, they are good for ensuring
certain types of data integrity. For example, it would make the
database to stop situations like somebody trying to insert a record
referring customer #9865 but in fact #9865 doesn't exist, whether it
was an unintentional user error or a bug in the application.


 Hopefully that is always possible - retrieving EXACTLY what was stored
 in the database. Why would one want the database to manipulate (change)
 data ? Is that a solution for lazy programming ?

No, in many situation, it's a more secure method. Databases can have
privileges set. You could have triggers and stored procedures that
update certain records that cannot otherwise be altered by the
application which can be written by a third party. For example, a
stored procedure would require both a debit and credit account for
transferring funds and/or checks that the actual amount is present
before doing it. Without this, a bugged application or rogue user/dev
who run the app with privleged access would be able to transfer funds
that don't exist.


 Simplicity and good design makes applications fast.

For some apps, fast is king. For some, data security and integrity is
ultimate. Would you want your banking transactions to run faster by
stripping out security and validation checks, at the risk that some
dude can transfer all your money into somebody else account? If so,
please let me know your bank account details and access credentials, I
have a program to speed up your banking transactions... ;)

 The integrity of the data can be divided into two aspects: ensuring the
 data remains constant (unaltered) while stored, which is the
 responsibility of the operation system and the database software, and
 the data's integrity from an application perspective. Junk-in always
 causes Junk-out even when using 'non-dumb' databases :-)

And if the database can further ensure that the application cannot put
junk in, whether due to a bug, user error or deliberate fraud, why
not? Especially when it's likely to be faster because it's native
code.
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/16/11, m.r...@5-cent.us m.r...@5-cent.us wrote:
 I've done a lot of what we used to call embedded SQL, and when I did do a
 join, it was *not* an explicit join. I've also used right or left once?
 twice? ever? But then, I carefully design and code my queries.

So it's more like a series of select a,b,c from x where d=y, then
select a2,b2,c2 from x2 where z=a? I'm just curious, not that I
think it's wrong because I'm actually leaning towards this. There were
many occasions where I find that breaking up complex queries and doing
filtering within my code was faster than trusting the dbms to optimize
the query.

One place I
 worked, someone else would run a query, and it would bring a server to its
 knees: I and a co-worker looked at it at one point, and it was a nightmare
 of joins, multiple references, etc, etc.

I had that kind of experience before, nightmare to figure out exactly
what the original coder was trying to do and a performance hell.

 But then, third normal form is, in general, idiotic except in the design
 phase. After you've decided on individual data, then collect them into
 records (oh, sorry, I'll have to do penance for not using the correct
 theological term, tubles).

lol, despite my formal education, I never got used to calling them
tuples. It just sounds too much like a nonsense word to me, and it
confuses the hell out of most people compared to records and rows.

One table for one major set of info, and a key
 or two across several. Classic is an entire year's monthly payments for
 one customer on *one* record, not 12 records, as it would be in third
 normal.

I'm actually leaning towards highly normalized schema but instead of
doing joins in queries, I'd do it in my application code. I haven't
formally tested and benchmarked things but it would seem that getting
the dbms to return 10 matching rows from a 1 million row table of say
100 bytes rows, then calling for 10 records matching those rows out of
another 1 million 1KB rows, is going to be a lot faster than letting
the dbms attempt to create a 1 million 100bytes x 1 million KB product
just to pull those same 10 rows. Unless the dbms' internal
optimization logic works every time. Maybe somebody with better
understanding of mysql/postgresql innards can shed some light on this.
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/16/11, m.r...@5-cent.us m.r...@5-cent.us wrote:
 You *need* both. Take too long, and the user will go somewhere else.

Of course :D

 I remember hearing about another division, a bunch of years ago, when I
 worked at the Scummy Mortgage Co. (name available upon request, offline),
 where the manager had designed the interface... and all the clerks *hated*
 it, and did everything they could to *not* use it.

 In other words, it was a failure. But then, that's another reason I have
 always wanted, during the design phase, to talk to the actual end users,
 *not* to the Manager Who Knew, I Mean, Everything.

Similar experiences, but some bosses/managers just don't accept that
we have to talk to the people who will actually be using the interface
most of the time. I had customers who told me it's a waste of time
talking to the workers because they don't understand the whole
operational process and insist we build it the upper management way.
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/16/11, Always Learning cen...@u61.u22.net wrote:
 Data is generally stored once. However because of legal requirements a
 customer's invoicing name and address and delivery address will be
 copied from the customer file and permanently stored in an invoice's
 header record. This means when the customer's record details are
 changed, the invoice continues to show the original name and address
 data valid at the time of creating that invoice.

 Each table as a unique reference number.

 A simple retrieval illustration ...

 select * from p2 where p2ref = '$p1ref' 

 select p3surname, p3forename, p3add1, p3add2, p3add3, p3add4 (etc) from
 p3 where p3customer = '$e7customer' 

 select w1note from w1 where w1date = '$s5date' 

This looks rather similar to what I am doing nowadays instead of
massive queries with sub-selects. Glad to see I'm not alone in this
direction. Hopefully this is a case of great minds think alike than
fools seldom differs! :D
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Re: [CentOS] Upgrade from 5.6 = 5.7

[Emmanuel Noobadmin]

On 9/16/11, Always Learning cen...@u61.u22.net wrote:
 Before anyone can add data for customer 9865, the existing customer
 record is displayed on the screen. This helps the user to be sure he/she
 has got the correct customer. A customer not found message means the
 record does not exist. Consequently it is impossible to add data to a
 non-existent customer record.

Assuming the system works as expected. Certainly I would expect the
application to be at least doing such basic validation and
verification. But wouldn't an added layer of safety be better? After
all, there could be race conditions where two or more users could
cause the application to pass the transaction to the database, which
results in more than the allowed amount being transacted because the
individual values were valid when the application checked.


 In most circumstances, instead of entering anonymous un-meaningful
 digits to identify customers, look-ups are done with postal code or
 partial address match or partial organisation name match or partial
 telephone number match etc. I love easy-to-use user-friendly systems.

Which is where AJAX comes in. Typing in a partial address or postal
code brings up, almost instantly on LAN environment, matches without
having to go to a search page or equivalent.

 I use the SQL privileges for tables and enable only the SQL verbs
 required by a user. I certainly do not want a user being able to 'drop'
 a table. Only I can do that.

I wasn't referring to that kind of problems but normal INSERT/UPDATE.

 In my systems such actions could not happen. No user gets permissions
 they do not genuinely require. If the programme specification says no
 'overdraft' then funds can not be transferred out of an account if that
 account balance would go negative.

Assuming everything works as expected, no bugs, no intentional hacks
and nobody edited the application source without your knowledge ;)

I think part of the difference in mentality is the environment our
applications run in. I always have to worry about some admin in the
client's office who thinks they know how to program, and clients
wanting to save money, asking them to do some modifications which may
lead to problems that I might get blamed for.

So having that added layer of checks at the DB level should help... at
least hopefully when the other guy gets an sql error, he might look
more carefully at what's wrong with his code instead of trying to
delete my trigger/constraints :D

 Database intervention to validate data is too late, in my opinion. You
 do not want junk getting pass the application's data input stage. If you
 want an amount of money and someone specifies the currency as GBQ
 instead of GBP, then that input error should be identified and rejected
 at the data input stage not actually sent to the database to be stored.

It's never too late to stop junk from getting stored. Early prevention
might be better than late prevention, but any prevention is definitely
better than none! :D

 That is why I always try to wreck my programmes by entering invalid
 data.  If I fail to wreck my programmes there is a reasonable certainty
 others will fail too.

But it doesn't guarantee that somebody/something else can't. After
all, we're only humans and I believe all of us have blind spots which
can allow edge cases to escape testing.
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Re: [CentOS] Vitualization and Partitioning

[Emmanuel Noobadmin]

Hi,

 When I do the install, do I or should I setup a separate partition for guest
That would be better from a performance point of view

 OS's? From the redhat docs, it looks like the guest OS's reside at
 /var/lib/libvirt/images/.
This should be using files as disk files, which I did and found it to
be a problem when there is heavy I/O.

I may combine my windoze XP on the CentOS machine
 so would I need to create a partition and format that at installation? If I
 decide to wait and go with Windoze 7 can I still create the partition later?

 I would like a partition scheme that allows for easier upgrades or installs
 without losing data.

Try using LVM then, it allows you to create and resize logical
partitions, including expanding with additional hard disks in the
future without having to reconfigure your VM guest (except the usual
file system expansion steps)

 Thanks, I'm more confused now that when I started reading about this stuf..

That's my experience too, the more we read, the more
alternatives/options there are, the more confusing it gets! :D
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Re: [CentOS] Have not had any updates to Centos 5.5

[Emmanuel Noobadmin]

On 9/8/11, Always Learning cen...@u61.u22.net wrote:
 (1) Many of us on 5.6 have installed to /etc/yum.repos.d an extra file
 for an extra, probably temporary, new repository called 'CR'.  Unsure
 what CR means but it might be 'Continuous Revision'.

Sorry, I just couldn't resist pointing out that it's Continuous
Release like it says in your #3 ;)

 (3) The contents of the CR repo are (the file name is your own choice):-

 # CentOS-CR.repo
 #
 # The continuous release  ( CR ) repository contains rpms from the
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Re: [CentOS] Centos 5.6 : No YUM Updates ?

[Emmanuel Noobadmin]

On 9/3/11, Luigi Rosa li...@luigirosa.com wrote:
 Florin Andrei said the following on 02/09/11 21:51:

 http://lists.centos.org/pipermail/centos-announce/2011-August/017689.html

 Is there something similiar for CentOS 6?

There was supposed to be a CR for 6 as well, at least I saw it
mentioned a few weeks back but searching now, it doesn't seemed to
have materialized.
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Re: [CentOS] please help

[Emmanuel Noobadmin]

On 9/2/11, Liang Arsalan manact...@gmail.com wrote:
 i am a user of windows and use little bit ubuntu
 my friend told me to use centos for web development
 i have question that what is features of centos.
 thank you

If there is no specific benefit for you to switch to using CentOS for
web development, then just stick to Windows. It would be far more
productive than for you.

Unless your friend was talking about web hosting rather than purely
web development.

If you are just looking to deploy a single website, then you might
also consider a ready-made CMS like Wordpress, Drupal or Joomla on a
shared hosting platform.
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Re: [CentOS] Apache warns Web server admins of DoS attack tool

[Emmanuel Noobadmin]

On 8/26/11, Always Learning cen...@u61.u22.net wrote:

 On Thu, 2011-08-25 at 14:36 -0700, John R Pierce wrote:
 the existing EL httpd.conf includes /etc/httpd/conf.d/*.conf  and any
 changes are expected to be made there rather than editing the stock file.

 Hi John,

 No Centos updates are likely to interfere with my Apache server options
 and virtual hosts. The existing /etc/httpd/conf/httpd.conf is large and
 laborious to read and fully understand especially with so many useful
 comments.

 'including' the parts that do change and are not operating system
 dependant, meaning putting them somewhere which has no connection to the
 operating system, for example

   /data/config/apache/server.conf
   /data/config/apache/domain.*

 means, I believe, that if a change to one small file goes wrong then
 there is absolutely no danger to 'damaging' any of the other files and
 the source of the problem is quick and easy to identify. Thus 'change
 damage' is strictly limited to one small self-contained file and can not
 affect any of the other files.


 I have too much experience of so-called collateral damage inadvertently
 caused to other parts of a file being changed. It costs time and money
 to trace and diagnose problems, so economically it is a good idea to
 eliminate as much as possible non-involved configuration parameters.

 As you will have noticed Apache actually offers the ability to fragment
 configuration parameters to other files by supplying - for the benefit
 of people like me - the 'include' facility.  If Apache never wanted
 folks to use this useful facility, it would never have offered the
 'include' ability.

I think you're misunderstanding John there? Rather than suggesting
using a single large httpd.conf file,  he seems to be just pointing
out that the default config already includes any *.conf files inside
the conf.d directory so you could just add the additional/sub .conf
files in there for consistency.
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