[CentOS] Manually mounting partitions in "linux rescue" mode

Tue Aug 3 08:53:23 UTC 2010
Robert Grasso <robert.grasso+nv at cedrat.com>


as for understanding the grub disk and partition numbering scheme, you should read :

info grub

and more specifically the "Naming convention" paragraph.

Your issue is all about understanding this.

Hope this helps

Robert GRASSO – System engineer

15 Chemin de Malacher - Inovallée - 38246 MEYLAN cedex - FRANCE 
Phone: +33 (0)4 76 90 50 45 - Fax: +33 (0)4 56 38 08 30
mailto:robert.grasso at cedrat.com - http://www.cedrat.com  

> -----Message d'origine-----
> De : centos-bounces at centos.org 
> [mailto:centos-bounces at centos.org] De la part de Edward Diener
> Envoyé : 3 août 2010 06:08
> À : centos at centos.org
> Objet : [CentOS] Manually mounting partitions in "linux rescue" mode
> I boot from the installation DVD, with an already existing CentOS 5.5 
> system on my hard disks. I have separate boot, root, and home 
> partitions. I have moved the boot partition and now I need to 
> re-initialize grub from rescue mode.
> Attempting to use 'rescue mode" to automatically mount my 
> system under 
> /mnt/sysimage eventally fails with an error message, which 
> essentially 
> says 'mount error' and nothing else. I am then put at a 
> command prompt 
> as root.
> So now I decide to manually mount my partitions at /mnt/sysimage and 
> then do a chroot to /mnt/sysimage. This succeeds and when I 
> look at my 
> files they are there.
> I now try 'grub' and the 'grub' shell comes up. I now attempt 
> the 'grub' 
> command:
> root (hd0,9)
> only to be met with:
> Error 21: Selected disk does not exist.
> I do not know what this means and how I can correct it. Does anybody 
> know what is going on ?
> One thing I am concerned about is that when I booted from the DVD and 
> was eventually put at the command prompt, I saw there were devices in 
> the /dev subdirectory but after I did the chroot, there were 
> no devices 
> in the new root's /dev subdirectory although when I had previosuly 
> booted into CentOS 5.5 on my hard disk off course they were there.
> The other thing I noticed is that after the 'chroot' the 
> 'mount' command 
> showed only my root partition mounted on /dev/sdb8 where it actually 
> exists ( along with sysfs and proc which I mounted from the 
> old root ). 
> But despite this there are no subdirectories under the new 
> root's /dev.
> I am just trying to re-initialize 'grub' so I can boot my CentOS 5.5 
> system again. There must be a way to successfully do this from the 
> installation DVD. If somebody can give me the steps to 
> manually mount my 
> partitions and succeed it would be very much appreciated.
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