Cobbler includes a pre-script for backing up ssh host keys durian an install. The script does the work of searching for your root partition in a less complicated way than the python example. I'll attach the script in case it's a helpful example.
Bryan Schneiders
bschneiders@xxxxxxxx
301-562-1900 ext 305
Shabazian, Chip wrote:
If you will have access to the network before and during the upgrade,
you could probably gather the partition/LVM information before the
upgrade, post it somewhere, wget it in the %pre and use it to mount your
drives. I haven’t tried any of this, but common sense tells me it
should be doable.
*From:* kickstart-list-bounces@xxxxxxxxxx
[mailto:kickstart-list-bounces@xxxxxxxxxx] *On Behalf Of *Matt Rose
*Sent:* Tuesday, August 25, 2009 11:27 AM
*To:* Discussion list about Kickstart
*Subject:* Re: CentOS upgrade - access to chroot in %pre?
quick, non-tested sample code to give you an idea, the following *WILL
NOT* work on your machine, unless you're really lucky and have your
root partition as the second partition on the first hard drive.
Even if it does work, it won't really do anything.
%pre --interpreter /usr/bin/python --erroronfail --log=/tmp/kspre.log
import sys,os,time,shutil,parted,re,subprocess,zipfile
sys.path.append("/usr/lib/anaconda")
import isys,iutil
### This finds the first hard drive
drive = isys.hardDriveDict().keys()[0]
### The following will mount the second partition on the first harddrive
as /tmp/sysimage
rootloc = "/tmp/sysimage"
os.makedirs(rootloc)
rootdrive = "/dev/%s2" % drive
isys.mount(rootdrive,rootloc,fstype="ext3")
###The following does some work to set up a somewhat sane chroot environment
os.system("chmod 644 /dev/null")
isys.mount("/dev","/tmp/sysimage/dev",fstype="tmpfs")
isys.mount("/proc","/tmp/sysimage/proc",fstype="proc")
isys.mount("/selinux","/tmp/sysimage/selinux",fstype="selinuxfs")
###The following function lets you open up subprocesses in the chroot
environment
def chroot():
os.chroot(rootloc)
###The following runs an rpm command to check the release in the chroot
subprocess.Popen("rpm -qa
*release",preexec_fn=chroot,shell=True,stdout=subprocess.PIPE).stdout.read()
###Cleanup
isys.umount("/tmp/sysimage/dev")
isys.umount("/tmp/sysimage/proc")
isys.umount("/tmp/sysimage/selinux")
isys.umount("/tmp/sysimage")
Matt Rose wrote:
Yes, on upgrade, but it's not easy. You have to detect and mount the
partitions by hand. If you know some python, you can include the
anaconda libs and helper functions, but if you're just using sh, you'd
have one hell of a %pre script.
Matt
Moray Henderson (ICT) wrote:
Hi everyone,
Is it possible to make the /mnt/sysimage/... chroot available to the %pre script of a CentOS 5.3 upgrade?
Moray.
"To err is human. To purr, feline"
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#raw
# Nifty trick to restore ssh keys without using a nochroot %post
echo "Saving ssh host keys..." > /dev/ttyS0
keys_found=no
insmod /lib/jbd.o
insmod /lib/ext3.o
mkdir -p /tmp/ssh
drives=$(list-harddrives | awk '{print $1}')
for disk in $drives; do
DISKS="$DISKS $(fdisk -l /dev/$disk | awk '/^\/dev/{print $1}')"
done
# Try to find the keys on ordinary partitions
for disk in $DISKS; do
name=$(basename $disk)
mkdir -p /tmp/$name
mount $disk /tmp/$name
[ $? -eq 0 ] || continue # Skip to the next partition if the mount fails
# Copy current ssh host keys out to be reused
if [ -d /tmp/${name}/etc/ssh ]; then
cp -a /tmp/${name}/etc/ssh/ssh_host* /tmp/ssh
keys_found="yes"
umount /tmp/$name
break
fi
umount /tmp/$name
rm -r /tmp/$name
done
# Try LVM if that didn't work
if [ "$keys_found" = "no" ]; then
lvm lvmdiskscan
vgs=$(lvm vgs | tail -n +2 | awk '{ print $1 }')
for vg in $vgs; do
# Activate any VG we found
lvm vgchange -ay $vg
done
lvs=$(lvm lvs | tail -n +2 | awk '{ print "/dev/" $2 "/" $1 }')
for lv in $lvs; do
tmpdir=$(mktemp -d findkeys.XXXXXX)
mkdir -p /tmp/${tmpdir}
mount $lv /tmp/${tmpdir} || continue # Skip to next volume if this fails
# Let's see if the keys are in there
if [ -d /tmp/${tmpdir}/etc/ssh ]; then
cp -a /tmp/${tmpdir}/etc/ssh/ssh_host* /tmp/ssh/
keys_found="yes"
umount /tmp/${tmpdir}
break # We're done!
fi
umount /tmp/${tmpdir}
rm -r /tmp/${tmpdir}
done
# And clean up..
for vg in $vgs; do
lvm vgchange -an $vg
done
fi
# Loop until the ssh rpm is installed
if [ "$keys_found" = "yes" ]; then
while : ; do
sleep 10
if [ -d /mnt/sysimage/etc/ssh ] ; then
cp -f /tmp/ssh/ssh_host* /mnt/sysimage/etc/ssh/
logger "SSH-HOST-KEY copied to newly installed system"
break
fi
done &
fi
#end
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