CentOS upgrade - access to chroot in %pre?

[Shabazian, Chip]

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 at redhat.com
[mailto:kickstart-list-bounces at redhat.com] 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.re
ad()

###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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