[K12OSN] restore backup with chroot + grub-install

[Robert Arkiletian]

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