Re: [CentOS] backup question
Gergely Buday wrote:
Dear CentOs users,
I have a centos server with nothing important at the moment, but I
would like to install some web-based project management tool (trac for
the curious) that would contain important data. And, as my network is
growing the configuration of the server is becoming complex. I would
like to have a proper backup so that I can restore the whole system
easily, should any problem occur. What do you recommend?
I'm not an expert on this, so my first idea is that I could do a per
application backup and create a tar file of the /etc. The latter
especially could be too naive. And, a push-the-button method that
handles all in once, not depending on the app number would be much
better.
Another thing: how I could do this to be safe across a centos upgrade?
I use dump (and restore). It works nice for ext3 file systems.
First you do a full dump (level 0) then you do an incremental dump (1 or
higher):
dumplevel=0
or for incremental
dumplevel=1
# To use ssh to connect to the remote host
export RSH=ssh
# then dump
dump -${dumplevel} -u -z -f remote_host:/sda1_dump /dev/sda1
You have to fill in your device and filename of course
See man dump/restore
Cheers,
Theo
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Re: [CentOS] mdadm on reboot
drew einhorn wrote: Hi, I'm in the process of trying mdadm for the first time I've been trying stuff out of tutorials, etc. At this point I know how to create stripes, and mirrors. My stripe is automatically restarting on reboot, but the degraded mirror isn't. Did you create /etc/mdadm.conf ? echo DEVICE /dev/sd* /etc/mdadm.conf mdadm --brief --examine /dev/sd* /etc/mdadm.conf Check the raid with cat /proc/mdstat It tells you which devices are part of the array. Finally put the raid flag on the partitions. I'm not sure whether it's really needed, I just do it: parted /dev/sda set 1 raid set 2 raid print 1 0.031101.975 primary ext3boot, raid 2101.975 194474.355 primary raid quit Theo ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] How to move my MBR
Scott Moseman wrote: I removed an ATA drive (/home) for a new SATA and my system would not boot. I'm guessing that it put the MBR on that drive instead of the drive that holds the / partition. What's the best way confirm where the MBR resides and, after I verify that's my problem, how I can move (or make a copy) onto a different drive? The BIOS determines which disk (the first) will be chosen to boot from. Sometimes hitting F12 or some other key gives you a menu to choose from. I have seen occasions were the bios was confused on what the default first disk was. Removing the last disk, booting, adding the disk would than help. To make a plain bootsector copy: dd if=/dev/sda of=/dev/sdb bs=512 count=1 But that the fist step of the boot loader. Next it will try to load the grub menu etc. from some disk (need not be the same disk, but mostly this disk contains a small (100MB) partition that holds these files and the kernel and ramdisk images. After boot this partition is normally mounted under /boot (for easy maintenance). So just copying the boot sector gives you only a grub prompt and then it stops. So try boot with a rescues disk (or LiveCD) so that you can study your disks. To install grub after booting from a resuce CD, you can use: grub root (hd0,1) # press tab for command completion setup (hd0) With all these examples you need to verify of course which disks/partition (sda/sdb etc) you need to choose. One way to search is to enter grub and use the find command with command completion: Probing devices to guess BIOS drives. This may take a long time. GNU GRUB version 0.95 (640K lower / 3072K upper memory) [ Minimal BASH-like line editing is supported. For the first word, TAB lists possible command completions. Anywhere else TAB lists the possible completions of a device/filename.] grub find (hdTAB Possible disks are: hd0 hd1 hd2 hd3 grub find (hd0,(TAB Possible partitions are: Partition num: 0, Filesystem type is ext2fs, partition type 0x83 Partition num: 1, Filesystem type unknown, partition type 0xfd grub find (hd0,0)/TAB Possible files are: lost+found vmlinuz-2.6.21-1.3194.fc7 grub System.map-2.6.21-1.3194.fc7 config-2.6.21-1 .3194.fc7 initrd-2.6.21-1.3194.fc7.img config-2.6.9-55.0.6.ELsmp initrd-2.6.9-55.0.6.ELsmp.img System.map-2 .6.9-55.0.6.ELsmp vmlinuz-2.6.9-55.0.6.ELsmp initrd-2.6.9-55.0.6.ELsmp.img_vg_new initrd-2.6.9-55.0.6.ELsmp .img_noraid grub find (hd0,0)/ Theo ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
[CentOS] NFS subdirectory on client is out of sync
Today a user asked me whether a file on one host can be different on another host. I was busy composing an answer to tell that the /home space on all clients are mounted using NFS from the file server. Any host will therefor see the same file. The user pointed me to his file and I copied this file from the client and compared this with the file on the file server. To my surprise it turned out that he was right, the files were different. I created a new file in this directory and it was not created on the file server. I renamed the file, and that was only seen on this single client. How can this happen? My setup file server (arend) CentOS release 4.6 # grep /home /etc/exports /home*(rw,sync,no_subtree_check) On the clients (also CentOS release 4.6) I mount /home with these options: arend:/home /homenfs proto=tcp,nfsvers=3,bg,defaults0 0 To debug I created (su stbo) on the client small test files (touch test) in each directory all the way to the user /home dir. It turns out that one subdirectory and everything below was not synchronized to the server. I could create files, move them, but it was just as if I was working on a local disk. Other users did not experience any problem on this machine so it was only one sub-directory (and everything below). I checked the syslog both on the client and on the server, but no messages of interest. [EMAIL PROTECTED] ~]# stat /home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd File: `/home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd' Size: 53214 Blocks: 112IO Block: 4096 regular file Device: fd01h/64769dInode: 6614395 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 635/stbo) Gid: ( 635/stbo) Access: 2008-05-14 12:46:34.0 +0200 Modify: 2008-05-14 10:08:07.0 +0200 Change: 2008-05-14 10:08:07.0 +0200 I renamed the filename on the client and did stat there as well. The modify time shows this file is indeed older as the user mentioned. [EMAIL PROTECTED] /root]$stat /home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd_theo_test File: `/home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd_theo_test' Size: 53214 Blocks: 112IO Block: 32768 regular file Device: 14h/20d Inode: 6583089 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 635/stbo) Gid: ( 635/stbo) Access: 2008-05-14 12:47:07.0 +0200 Modify: 2008-04-09 13:09:23.0 +0200 Change: 2008-05-14 12:24:24.0 +0200 After rebooting everything is normal again: [EMAIL PROTECTED] ~]# stat /home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd File: `/home/stbo/workarea/toekan/design/dig/vhdl/fpga/fpga_top.vhd' Size: 53214 Blocks: 112IO Block: 32768 regular file Device: 14h/20d Inode: 6614395 Links: 1 Access: (0664/-rw-rw-r--) Uid: ( 635/stbo) Gid: ( 635/stbo) Access: 2008-05-14 12:46:34.0 +0200 Modify: 2008-05-14 10:08:07.0 +0200 Change: 2008-05-14 10:08:07.0 +0200 Any clue what could have gone wrong? Since I trust on a working NFS, I like to understand what could have gone wrong. Any suggestions are welcome. Thanks, Theo ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Securing SSH
Tim Alberts wrote: So I setup ssh on a server so I could do some work from home and I think the second I opened it every sorry monkey from around the world has been trying every account name imaginable to get into the system. What's a good way to deal with this? ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos You could consider to disallow password access. Use only public key authentication. The attacks will remain, but can never succeed. (The scripts are not smart so they keep trying for hours sometimes) sshd_config: PasswordAuthentication no Now create a public/private ssh keypair and put the public key in ~/.ssh/authorized_keys on the remote machine. # local machine* ssh-keygen -t dsa* *scp** ~/.ssh/id_dsa.pub remote_host:.ssh/authorized_keys *# remote host* **chmod 600 ~/.ssh/authorized_keys chmod 700 ~/.ssh * To be really save, only allow access from a limited number of IP addresses: ** cat ~/.ssh/authorized_keys from=123.345.133.123,home.com,work.com ssh-dss B3NzaC1kc3MAsnipAqNY= [EMAIL PROTECTED] Theo ___ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
Re: [CentOS] Dump on remote filesystems?
Scott Ehrlich wrote:
I have a couple C5 systems I want to back up. My plan is to, one way
or another, back them up to a C5 machine in my office. I have samba
installed on the systems to back up, the machines are mounted on the
system in my office, and a tape library hanging of the system in my
office.
I was hoping to perform a simple /sbin/dump of the remote systems. I
put together a script for another successful backup I have going on a
system with local filesystems. But for remote filesystems, I get
errors of File Cannot Be Accessed (//remote_system/subdir) which does
exist as an smb mounted filesystem.
I'd use NFS, but I would like a bit more control and some level of
encryption for the user authentication and data being transferred.
If a direct dump of remote smb filesystems isn't possible, I may opt
to have each system perform their own local dumps, then run a script
locally on the tape-connected machine to dump those local dumps, or
copy the dumps locally then dump them to tape.
If nothing else works, I can always install Windows XP and use Windows
backup program, but I'd really like to try and get this going under
Linux before going that route.
Thanks for insights.
Scott
What you could do is to dump from the remote machine to the main backup
machine. For this to work I work with ssh keys (no password needed).
The example assumes the backup is started from the remote host. But in
principle it can also be initiated from the backup server using ssh.
SRC_SERVER=this_hostname
BAK_SERVER=backup_server
DATE=$(date +%Y%m%d)
dumplevel=0
export RSH=ssh
ssh $BAK_SERVER mkdir -p /backup/${SRC_SERVER}/${DATE}_${dumplevel}
# file needs to exist
backup_file=/backup/somefile
ssh $BAK_SERVER touch ${backup_file}
dump -${dumplevel} -u -z -f $BAK_SERVER:${backup_file}
/dev/VolGroup00/VolGroup00
Theo
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