CENTOS boot over raid partition

Thomas Neumann blacky+fai at fluffbunny.de
Tue Nov 25 08:57:01 CET 2014

On Tuesday 25 November 2014 09:16:28 Antanas Masevicius wrote:
> Yes, thats a solution, but still, it would be better to have some kind of
> automation. One way probably would be to run some kind of configuration
> engine, or write some script fixing md mbr from init.d. How would you do
> that?

During/after installation of a new machine:
  install mbr on second disk and never touch it again

_After_ successfully booting the new kernel:
  synchronize contents of /boot to second disk
  (adjust hd0 / hd1 as necessary)

Implement this is as a small script but _never_ call this script automatically 
_during the installation of a new kernel package_. (This prevents promoting a 
logical error to your backup /boot filesystem.)

If you want to fully automate it then you could add this script to be run from 
/etc/rc.local or similar. If you've reached this stage you can be reasonably 
sure the kernel has managed to boot and mount all required filesystems. 
(However there's no guarantee the network works as expected, so you should 
make sure the relevant modules are included in the initrd or have console 
access available.)

Yes, this is a bit more work then trying to get a software-raid /boot to work. 
But it has 2 distinct advantages:
 - if something accidentally deletes / corrupts a file in /boot there's
   still a reasonable chance for recovery _during system boot_
 - it works with all combinations of fat/gpt/md/lvm/crypt/btrfs

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