[CentOS] "yum update" did not update kernel on one box

Mon May 12 14:52:16 UTC 2008
Ross S. W. Walker <rwalker at medallion.com>

lannyma at gmail.com wrote:
> On 5/8/08, Kai Schaetzl <maillists AT conactive DOT com> wrote:
> <snip>
> > hda3 and hda9 are your Linux LVM partitions, maybe they belong to one volume
> > group, I don't know (your fstab would tell more, there's also a graphical
> > frontend for LVM in your desktop).
> >
> > From your grub.conf we know that it thinks it's installed on (hd0,2), but
> > hd0,2 is hda3 (if I understand that correctly) and that is LVM, and grub
> > can't boot from LVM because grub boots the kernel and only that knows about
> > LVM. So, you are probably booting from hda8, but it's not in your fstab as
> > the  /boot partition.
> >
> > What does a "df" say? Does it list hda8 among the partitions? Probably not?
> [root at compaq1300 ~]# df
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dev/mapper/VolGroup00-LogVol00
>                       10696956   4597688   5547128  46% /
> /dev/hda3               102486     22174     75020  23% /boot
> tmpfs                   257260         0    257260   0% /dev/shm
> [root at compaq1300 ~]#
> > Mount it and have a look at that partition, does it contain the same stuff
> > as your /boot partition? If not mounted, do:
> > mkdir /mnt/hda8
> > mount /dev/hda8 /mnt/hda8
> > cat /mnt/hda8/boot/grub/grub.conf
> > Does this look like the grub.conf that is the *real* one booting your system?
> [root at compaq1300 ~]# mkdir /mnt/hda8
> [root at compaq1300 ~]# mount /dev/hda8 /mnt/hda8
> [root at compaq1300 ~]# cat /mnt/hda8/boot/grub/grub.conf
> cat: /mnt/hda8/boot/grub/grub.conf: No such file or directory
> [root at compaq1300 ~]#

The proper location of the grub.conf is:


'boot' was the name of the mount point which isn't part of the 'boot' file system.

> Kai:  Before I got the above data this morning, I let PUP
> download/install the latest kernel (2.6.18-53.1.19.el5.i686) but after
> rebooting, it comes up with the original kernel that is on the CentOS
> 5 Install DVD  I used last November. Not surprising that it does not
> boot this newest kernel. The download/install seemed to go perfectly,
> so the "Subject" changed from yum not updating the kernel to where is
> the proper boot file.... When it boots Linux, CentOS gives a message
> something like booting root (hd 0, 7). TIA, Lanny

Kai, is right though, chances are grub from the MBR is looking into a
different partition for it's config and shows one of the problems with
grub. I think there is a version of grub that will keep it's configs
in the remaining sectors (sectors 2-62) of the first track and boot
the kernels directly from another partition, but that's non-standard.

You could use a single 'boot' partition for all your Linux distros
though, but make it bigger, say 256MB (or 512MB if you have a lot
of distros installed).

I would typically have /dev/hda1 setup as a 256MB 'boot' and reuse it
for other distros, just make sure not to format it on install or you'll
bork the first distro's kernels!


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