Howdy and thanks for the comments :-)
*Chainloader.*
Think of it in terms of a RUN command in the order of 'a chain of
links', i guess that is the easiest way to explain it.
chainloader implies - 'to load the boot manager by command' in a similar
way to any other filesystem object. i.e. "now you have switched me on my
first order of the day is to ...."
The +1 is a directive to order it to complete this task.
So in plain english, what we are asking grub to do is to simply 'engage'
or load the first sector of the disk we named in the root.
*root(hdX,y)*
where 'x' is the hard disk number and 'y' is the partition.
If you were running a single hard disk with multiple o/s then you would
address root (hd0, X) where x is the partition number based on examing
the structure offered by gparted or the windows disk manager. Grub does
not have to exist in the root partition with MBR - in fact NEVER write
GRUB into the first few sectors of your disk on a dual-boot scenario.
Add grub to a differnet partition - i.e. (hd0, 2) where windows would be
in (hd0, 0) and (hd0, 1)
Having read through the grub paperwork I did experiment with the
rootnoverify command line but found this to be a little erratic if not
dangerous to the overly sensitive MBR at times as it does not mount the
disk based on any factual evidence, whereas 'Root' will mount the drive,
estimate what it is looking at and passes this information to the
chainloader command.
*makeactive*
reset the active partition, the one we called in root(x,y) to be active
in grub.
*map*
Mapping is a simple method of fooling windows into believing it is the
first disk. Another MS monopoly foiled so to speak!
A map is created on two lines - i.e.
map (hd0) (hd1) (hd2) (hd3) (hd4) etc...
map (hd1) (hd1) (hd2) (hd3) (hd0)
where line 1 in the above example is a structure of your disk drives as
represented by the boot process in your BIOS.
so your first line of the map should match your BIOS but where bios
labels them 1-X, map begins with 0-X. So a drive in BIOS called 1 is 0
in your map.
The second line instructs the chain to re-align the BIOS mappings in
such a way as to determine a new load order that is required for a
multiboot system.
So if we have the following physical structure:
O/S BIOS NUMBER MAP NUMBER
DEBIAN 1 0
WIN XP 2 1
WIN 2K 3 2
VISTA 4 3
Then Debian will be our root disc containing the grub mechanism. Your
system will auto boot to this O/S if you ignore any prompts!
But, if you hit ESC when prompted by GRUB and choose VISTA [god help us!]
Then we are re-mapping the computer in such a way as to rebuild the
default structure shown above:
O/S BIOS NUMBER NEW MAP NUMBER
DEBIAN 1 1
WIN XP 2 2
WIN 2K 3 3
VISTA 4 0
And when this happens, VISTA will believe it is the first disc and boot
without any issues whatsoever!
Note: This how-to implies the use of your default operating system being
a DEBIAN breed - i.e. ETCH GNOME, ECTH KDE, SARGE, MEPIS, UBUNTU,
KUBUNTU. MINT ETC.... do not try this in any Red Hat Distro [i.e.
fedora, centos etc...] - red hat handles grub in a different manner and
it isn;t as felxible as Debian - thus i like debian methodologies!
However, in saying that. There is no reason why fedora, centos or any
other Linux Distro cannot be in your DISK CHAIN replacing or adding to
the Windows examples above - it all depends on the how many SATA drives
you can run from your motherboard. I'm lucky - i build my own machines
and mine support over 10!
If i missed anything, just give me a shout.
But i can always go through this at the next meeting if anyone wants me to.
Yes i will be there this month!
J.
Richard Forth wrote:
what does chainloader +1 mean/do?
ps nice how to!
Rich
On 15/03/2008, *substation* <[EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Hi people,
RE: UBUNTU/DEBIAN MULTI-BOOT SATA SYSTEMS - ISSUE FIX
For anyone who is interested here is a great way of being able to
multi-boot Ubuntu Gutsy/Debian Etch with Windows/Linux as often
and as many times as you need. No more changing cables!
This works with Linux acting as a master O/S for any Linux
Distribution or Windows operating system. This is because we are
going to modify GRUB.
The windows boot manager is not very flexible!
This method or approach can work for unlimited SATA disk drives
containing unlimited O/S systems and storage drives - you could
even use an ESATA disk - without the risk of killing your windows
MBR without the risk of disk failure killing your system - pretty
much risk free as long as you follow the how to carefully; but
mistakes can happen. S yes, this guide is without warranty and
works on a SATA based hard disk system only :-)
Note: For multiple IDE disks you need to reconfigure the
master/slave drive settings, whereas for a single disk multi-boot
system it is simple enough to simply install XP first then add
Ubuntu using a manual partition setup [there is a guide in
Ubuntu's community docs for this]. For this how-to i am NOT using
a RAID ARRAY and treating each disk as a separate disk drive for a
distinct O/S. If you did use RAID, then you need to treat your
disk like a rather large EIDE setup with partitions.
These instructions will create 3 separate operating systems and a
single hard disk for additional shared storage. Linux will always
be disk number 1 and for simplicity - my cross-O/S storage drive
is formatted to FAT32 - if you want to use NTFS then get the
relevant disk tools for your linux distro!
Let's begin:
1] If you need to install your O/S jump to point 1, otherwise skip
to point 2.
1a] If you need to install an operating system, unplug all your
disk drives. Add a single drie to header/channel 1 and install on
a one-at-a-time.
2a] Repeat the above for each and every O/S
2] Back-up your data - The Windows MBR is very touchy.
Then take your existing operating system disks and attach them in
the following order to your sata headers on your motherboard:
HEADER/Channel
1 UBUNTU
2 WINXP
3 WINXP
4 STORAGE DRIVE
I find it easier to add the storage drive at the end, but you may
want to run it as disk 2.
All windows computers will see each others hard-disk whilst linux
can see them all.
All operating systems are standalone and fully functional.
3] Verify your BIOS can see all the disks and ensure you have them
booting in the correct order
4] Boot to UBUNTU, open terminal and either:
$ sudo vi /boot/grub/menu.lst
or
$ sudo gedit /boot/grub/menu.lst
Create a back-up of this file immediately then start editing.
4] Scroll down to the bottom of this file and look for the final
line - i.e.
### END DEBIAN AUTOMATIC KERNELS LIST
Below that line type the following [use a tab to separate the
command word and the statement]:
title Other operating systems:
root
5] Now lets add your O/S. Your file should now look like this:
### END DEBIAN AUTOMATIC KERNELS LIST
title Other operating systems:
root
Below this type the following replacing XXX with your O/S
descriptions [use a tab to separate the command word and the
statement]:
title XXXXXXXXXXXXXXX XXXXXXX XXXXXXXX
root (hd1,0)
makeactive
chainloader +1
map (hd0) (hd1) (hd2)
map (hd1) (hd0) (hd2)
title XXXXXXXXXXXXXXX XXXXXXX XXXXXXXX
root (hd2,0)
makeactive
chainloader +1
map (hd0) (hd1) (hd2)
map (hd2) (hd1) (hd2)
Now, let's adjust the timeout for something more human. Look for
the following line at the top of the menu.lst file:
timeout 3
Change the number to something suitable - i.e. 9 to give you a 9
second breaker.
Jone done.
Save the file and reboot. Jump to point 6 below.
===============================
Notes:
Your edited file could look like this:
### END DEBIAN AUTOMATIC KERNELS LIST
title Other operating systems:
root
title Windows XP, Games
root (hd1,0)
makeactive
chainloader +1
map (hd0) (hd1) (hd2)
map (hd1) (hd0) (hd2)
title Windows 2000 Server
root (hd2,0)
makeactive
chainloader +1
map (hd0) (hd1) (hd2)
map (hd2) (hd1) (hd2)
What we did:
root (hd2,0) - This line simply references the disk number and
the correct partition.
In what we have done, the important part is here:
map (hd0) (hd1) (hd2)
map (hd2) (hd1) (hd2)
To fool XP we have created a map of the disks starting with disk
drive 0 [where your first disk is disk 0]
So fo you need to add more disks, replicate the above template as
many times as required by following the implied logic and adding a
new map - i.e. (hd3), (hd4) etc....
===============================
6] If all goes well, simply watch GRUB. Hit the escape key when
asked and choose the relevant O/S to use.
If you have any issues - i.e. a stalled boot [flashing cursor or a
grub error] it is either [a] you made a typo or [b] check your cables.
If you really get stuck, don't force things. Simply switch off,
disconnect all drives except for Ubuntu/Debian
open terminal and try this command:
$ sudo fdisk -l
This should confirm if Linux can see all the hard disk on your system.
If the above is correct then re-check your work with
$ sudo vi /boot/grub/menu.lst
mistakes can often happen in GEDIT - so use VI [VIM] or NANO etc...
I like VI myself.
If nothing works at all and you are fed up - then something else
must be at issue, so simply restore your backup menu.lst file ,
disconnect the relevant drives and continue as before [no harm done].
===============================
As i said, this how-to is without warranty - as the Windows MBR is
very touchy!.
Be careful and have fun!
J.
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