[CentOS] How does Linux Repair actually work

Les Mikesell lesmikesell at gmail.com
Thu Mar 24 12:46:34 UTC 2011

On 3/24/11 2:59 AM, Simon Matter wrote:
>> Thanks to the help of folks on this forum, I now have my Centos 4
>> box up and working, however I do have a question on how the
>> repair actually worked.
>> After starting the Linux Repair, the process "found my installed
>> Linux".  Some of you will remember that I had accidentally erased
>> the /boot and /boot/grub directories, but I had most of the files
>> saved (not the symbolic links) and put them back into the
>> directories *and* I did run a rpm reinstall.
>> When Linux Repair "found the installed Linux", did it create a
>> new /boot and /boot/grub *or* did it just use what I had put there?
> When booting into "rescue" mode with the RH/CentOS installer disk, it
> searches for filesystems that look like a Linux installation and mounts
> them so you can fix them. The rescue system doesn NOT change anything -
> that was you who did it by running grub-install or whatever. So, I think
> nothing has changed in your /boot directory despite the things
> grub-install may have touched.

Yes, on CentOS4, I think you could have done the partition mounting by hand with 
the same results if you knew the layout.  On CentOS5 there is a little extra 
magic to populate the /dev directory so things still work after you chroot into 
the place where you mounted the root of the hard drive.  Grub-install just does 
some guesswork about the bios numbering that grub uses for devices/partitions, 
then runs grub with the right arguments to the root and setup commands.  You 
could have done that yourself too.

   lesmikesell at gmail.com

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