Re: CentOS 5 grub boot problem

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On 08/05/2015 04:41 PM, Chris Murphy wrote:
I do not know why there's a duplication of the install command.
...
   : Running... ['/sbin/grub', '--batch', '--no-floppy',
'--device-map=/boot/grub/device.map']
   : grub> device (hd0) /dev/vdb
   : grub> root (hd0,1)
   : grub> install --stage2=/boot/grub/stage2 /grub/stage1 d (hd0,1)
/grub/stage2 p (hd0,1)/grub/grub.conf

"device (hd0) /dev/vdb" overrides the data in device.map and instructs the grub shell to examine vdb where subsequent commands refer to (hd0).

"root (hd0,1)" sets the location where grub will look for the required files, probably stage1, stage2, and e2fs_stage1_5.

"install ..." checks for required files and writes a modified copy of stage1 to the first block of the device following 'd'. In your case, that should be the first partition on vdb.

https://www.gnu.org/software/grub/manual/legacy/grub.html#install

   : Running... ['/sbin/grub', '--batch', '--no-floppy',
'--device-map=/boot/grub/device.map']
   : grub> root (hd0,1)
   : grub> install --stage2=/boot/grub/stage2 /grub/stage1 d (hd0,1)
/grub/stage2 p (hd0,1)/grub/grub.conf


This will do the same thing, except that it will operate on /dev/vda.

In both cases, stage1's block list will refer to BIOS device 0 for the location of stage2, so that if the BIOS boots from that drive, grub will load stage2, and then the kernel and initrd from the same drive. That's not necessarily the case, though. Stage 2 could be on a different drive.
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