[CentOS] Re: how do i have a clone centos server

[Scott Silva]

on 3-31-2008 6:30 AM Toby Bluhm spake the following:
> Mail Administrator wrote:
>> Thnaks john,
>>
>> u gave me a  grt idea ..
>> the second one
>> seems quite interestin
>>
>> but i do have to get additional HDD and mirror my existing server which
>> has jus one disk
>>
>>   
> 
> This was my procedure to mirror an existing single IDE disk RH4 system.
> 
> YMMV. No guarantees. Not tested on Centos5. May eat all your data and 
> drink all your beer.
> 
> Make a total backup before doing anything.
> 
> IIRC the grub setup is what gave me the most problem.
> 
> Hopefully, someone will chime in to point out any flaws here.
> 
> ------------
> Current System/OS on single 10GB IDE disk
> /dev/hda2 = swap @ 1GB
> /dev/hda1 = / @ 9GB
> Current system/OS is not in an LVM volume.
> 
> 1. Install a 2nd identical disk as hdb
> 2. fdisk:
> /dev/hdb1 = 9000M ; /dev/hdb2 = 1000M ( rest of disk )
> part1 = type FD (raid)
> part2 = type FD (raid)
> 3. Create mirror device /dev/md10 for / with 2nd disk missing:
> mdadm --create --level=1 --force --raid-devices=1 /dev/md10 /dev/hdb1
> 4. mke2fs -j /dev/md10
> 5.  Create mirror device /dev/md11 for swap with 2nd disk missing:
>  mdadm --create --level=1 --force --raid-devices=1 /dev/md11 /dev/hdb2
> 6. mkswap /dev/md11
> 
>  It may be safer to start step 7 from a rescue disk.
> 
> 7. mkdir /z
> 8. mount /dev/md10 /z
> 9. cd /
> 10. dump -a0f - . | ( cd /z ; restore -xvf - )
> 11. Update pertinent lines in
> 
> /z/etc/grub.conf:
> splashimage=(hd0,0)/boot/grub/splash.xpm.gz
> root (hd0,0)
> kernel /boot/vmlinuz-2.6.9-11.EL ro root=/dev/md10 rhgb
> 
> /z/etc/fstab:
> /dev/md10       /       ext3    defaults        1 1
> /dev/md11      swap    swap    defaults        0 0
> 
> 12. Shutdown
> 13. swap hdb & hda around
> 14. Boot RHEL4 linux rescue ; let system find/mount RHEL Installations
> 15. fdisk hdb to be identical to hda
> 16. chroot /mnt/sysimage
> 17. grub-install /dev/hda
> 18. grub-install /dev/hdb
> 19. Setup grub:
> grub
> root (hd0,0)
> setup (hd0)
> quit
> 20. Create new initrd(s) to include modules raid, scsi, lvm, etc needed 
> at boot time:
> mkinitrd --with=raid0 --with=raid1 --with=raid5 --with=aic79xx 
> /boot/initrd-2.6.9-22.EL.img.new
> mv /boot/initrd-2.6.9-22.EL.img /boot/initrd-2.6.9-22.EL.img.old
> cp /boot/initrd-2.6.9-22.EL.img.new /boot/initrd-2.6.9-22.EL.img
> 21. Reboot to normal startup on the new mirrored / & swap.
> 
>  Step 21 needs to boot cleanly. Step 22 will remove your last chance to 
> revert to the old setup by installing the original boot disk as hda.
>  If something goes bad here, may need to restore from backup.
> 
> 22. Add in 2nd disk to md10 mirror set:
> mdadm --grow /dev/md10 --raid-devices=2
> mdadm --add /dev/md10 /dev/hdb1
> 
> 23. Add in 2nd disk to md11 mirror set:
> mdadm --grow /dev/md11 --raid-devices=2
> mdadm --add /dev/md11 /dev/hdb2
> 
> You can monitor the sync process:
> 
> cat /proc/mdstat:
> md10 : active raid1 hdb1[2] hda1[0]
>      8789632 blocks [2/1] [U_]
>      [>....................]  recovery =  0.8% (77952/8789632) 
> finish=5.5min speed=25984K/sec
> unused devices: <none>
> 
> 24. System will be at normal state when mirror sync is finished
> 
> 
One thing to add. Don't put the second drive as a slave to the first. Most 
times when a PATA drive goes down it will lock the entire channel until a 
reboot. The whole point of having the mirrors is to keep running on a drive 
fail. It is better to have it on the secondary master as hdc. Of course this 
doesn't apply to SATA or SCSI or their variants

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