[CentOS] Re: Stuck at GRUB

Christopher Chan christopher at ias.com.hk
Thu Nov 29 14:51:34 UTC 2007

Ugo Bellavance wrote:
> jancio_wodnik at wp.pl wrote:
>> Christopher Chan pisze:
>>>>>>> grub cannot find its second stage. Are you booting from a 
>>>>>>> mirrored partition?
>>>>>> Yes
>>>>> What could be a solution?  And what could have happen upon the reboot?
>>>> That is weird.  I just re-installed centos5 and it is now booting 
>>>> properly.  What could I do to avoid this situation in the future?
>>> IIRC, RHEL4 does not properly handle installation of grub on mirrored 
>>> partitions and therefore Centos4 suffers from the same problem.
>>> RHEL5 does it properly now as you can see. This has been a long 
>>> outstanding problem of anaconda.
>> Yeap, this is true. After installing centos4 on RAID1 disk (software 
>> raid) i always do:
>> grub
>> grub>device (hd0) /dev/hdc
>> grub>root (hd0,0)       grub>setup (hd0)
>> where /dev/hdc is second RAID DISK (it could be whatever: /dev/sdb1 etc)
>> So system is booting form first or second riad1 disk
> Ok, so to sum up from what I understand of my problem:
> Installation of CentOS4 -> Installs grub only on one HDD partition out 
> of 2, in the mirror.

Well, I believe you chose md0 or something to install grub on right?

> One disk fails, the one that has grub

Not necessarily. All it takes is a change in the sequence of disk 

> System won't boot because it can't find grub on the other drive.

Correct. It needs to be instructed to look on its own drive.

> If I had centos5 there in the first place, the setup would have taken 
> care of installing grub on the 2 mirrored raid partitions.
> Am I right?


> Is there a way to know where grub is installed?  I have a few servers 
> running in RAID 1 software for /boot, I gotta fix this.  If I can't tell 
> whether it is installed or not, is it dangerous to re-install it using 
> the command above?

So long as you have all the necessary grub files, there is not much 
danger. Even if you are missing a config file on this side of the mirror 
(impossible...) so long as you load grub stage 2, you will have the 
power you need to continue if you have access (eg: via serial)

More information about the CentOS mailing list