Modular Interactive Kickstart Madness pt. 2

This is Part 2. See Part 1 here.

Previously, we covered using a combination of %include files and an interactive pre- script to make Kickstart more flexible. Now we cover post-install customization.

The %post section

To make good use of the %post section, you should be aware of another quirk in Kickstart: by default, the %post scripts run in a different environment than the %pre scripts.

The Kickstart installer runs out of a temporary environment that exists in memory. During installation, Kickstart pushes content into a chrooted environment that is mounted under /mnt/sysimage/ . The %pre and main sections of Kickstart run from outside of the chroot, but the %post section runs from inside the chroot by default. This saves you from having to prepend ‘/mnt/sysimage/’ to every file path when you run your post content. If we need any of our Kickstart files to be available for the %post section, we will need to copy them into the chrooted environment first.

We do this by declaring two %post sections. The first %post runs outside of the chroot with the --nochroot flag, and we use it to push our content from Kickstart’s /tmp directory into /mnt/sysimage/tmp/ . The second %post section runs from inside the chroot, and we can work as if we are sitting in the installed filesystem. You only need one %end tag to cover both %post sections.

# Start a post section outside of chroot, so we can push kickstart files into chroot
%post --nochroot

# In the %pre script eariler, we mounted a NFS share to /tmp/kickmedia to pull down kickstart scripts
# Now we copy them into our chroot to access them within the installed environment
cp -r /tmp/kickmedia /mnt/sysimage/tmp/newkickmedia

# Start another post script (inside the chroot), and run your post-install routines.
# These are really running out of /mnt/sysimage/tmp, but the chroot lets us use normal file paths. 
%post --log=/root/ks.post_install.op --interpreter /bin/bash

/tmp/newkickmedia/postinstall.sh

%end #End post scripts

Like we did with the %include files, you can also use the %pre scripts to customize your %post scripts before they run.