[K12OSN] restore backup with chroot + grub-install
Robert Arkiletian
robark at telus.net
Sun Dec 12 00:19:17 UTC 2004
Les Mikesell wrote:
>On Sat, 2004-12-11 at 00:14, Robert Arkiletian wrote:
>
>
>
>>After some reading I'm going to take a guess. After I
>>1) fdisk the brand new drive to the same parameters as before and
>>2) then mke2fs -j the filesystem.
>>3) Then mount it (/dev/sda1) from gnoppix as /mnt/sda1
>>4) then untar my backup from mobile drive to the new drive
>>5) then chroot /mnt/sda1 /sbin/grub-install /dev/sda
>>6) then umount /dev/sda
>>
>>Line number 5 is the one I want confirmation on.
>>
>>
Does line 5 look okay?
>
>First make sure that you have /boot. It is usually on its own
>partition but could be just a directory under /.
>
Yup, /boot is just a dir in / (not a seperate partition)
> When you rebuild
>by hand it should be on the first partition on the drive to avoid
>any size limits in the bios boot code.
>
>
Yes, I know, / is on the first scsi drive /dev/sda1
>The original install will have put labels on the partitions. You'll
>either have to create matching ones with e2label or edit /etc/fstab
>and grub.conf to refer to the partition device names. Note that
>/etc/grub.conf is a symlink to /boot/grub/grub.conf so you have to
>edit the real location or wait until you have your new partitions
>mounted in their relative positions and chroot'ed to its root.
>
>
Yeah I noticed this label business. Here is fstab from the server
==========================================
LABEL=/ / ext3 defaults 1 1
none /dev/pts devpts gid=5,mode=620 0 0
LABEL=/home /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sda2 swap swap defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660
noauto,owner,kudzu,r
o 0 0
/dev/fd0 /mnt/floppy auto
noauto,owner,kudzu 0 0
==========================================
I thought it should have looked like
========================================
/dev/sda1 / ext3
defaults 1 1
none /dev/pts devpts gid=5,mode=620 0 0
/dev/sdb1 /home ext3 defaults 1 2
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/sda2 swap swap defaults 0 0
/dev/cdrom /mnt/cdrom udf,iso9660
noauto,owner,kudzu,r
o 0 0
/dev/fd0 /mnt/floppy auto
noauto,owner,kudzu 0 0
========================================
Would I still need to edit fstab and grub.conf if I chroot to the newly
mounted and untared drive and do a grub-install from there?
>You'll probably have trouble doing the chroot after booting a
>very different distribution CD. I'd recommend rebooting with
>the distribution's install CD with 'linux rescue' at the boot prompt
>after you have done the tar copy. If /etc/fstab on the restored copy
>matches your partition layout (using either names or labels), the
>boot in rescue mode will automatically mount the partitions for you
>and suggest the right chroot command to continue. You can probably
>do the re-install from a RH/fedora boot in rescue mode but a knoppix
>based CD is nicer and the reboot step gives you a nice sanity check.
>If it doesn't automatically mount the system under /mnt/sysinstall you
>know the problem is the mismatch between /etc/fstab and the partition
>names or labels and you should fix that before continuing.
>
>
Good advice Les thanks. But the reason I chose gnoppix (Ubuntu) is that
it has a relatively up to date adaptec aic79xx driver since it uses
kernel 2.6.7. If I use the RH9 install disc in rescue mode it has an
old/buggy scsi driver for the aic79xx. That's why I was scared to
tar/copy the entire fs with it. Needless to say I have the latest scsi
driver running on the server now but this was installed with an rpm
update. Reading your post carefully I can imagine myself using gnoppix
to fdisk and untar/copy to the new drive (with the advantage of the new
scsi driver) . Then as you suggest reboot again with the RH9 cd to
rescue and then finally just chroot and grub-install. Hopefully, I
should not have to mess with labels. Is this all correct?
>The only other trouble you might have would be if the target machine
>has a different scsi controller than the source. In that case you
>have to edit /etc/modules.conf (or conf.modules on older systems) in
>the CD boot/chroot step to change the scsi driver module and then
>rebuild the initial ramdisk with /sbin/mkinitrd.
>
>
Wow you really have experience Les! But if we had a catastrophy like a
burglary then I would repurchase the same components. I am mainly
afraid of the scsi drive dying. I would just go and buy the exact same
drive and restore. Feels good to have a backup.
--
Robert Arkiletian
C++ GUI tutorial http://fltk.org/links.php?V219
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