====== Interactive Post-install Script in Kickstart ======
===== About This Document =====
As of this writing, I'm just finishing up the process of setting up a PXE booting kickstart server (which I'm planning on doing a full writeup on soon).  After getting everything working, in terms of bare metal to installed OS, I got to the point of starting to tweak my kickstart configs.  And when I wanted to set up the network info on the newly created OS, I ran into a snag.  

At my current job, we have a few Red Hat/CentOS servers scattered about, but we are mostly a FreeBSD shop.  We already had a home-brewed PXE boot installer for FreeBSD that was originally cobbled together years ago, but after a recent merger we were starting to hear whispers of having to build out more RH/CentOS, so I figured I would hop on this mission as I was by far the best "Linux guy" we had.  Being that our FreeBSD installer was home-brewed, it was generally pretty simple to add in new functionality, as the install system was just a bunch of shell scripts.  I had built an interactive menu into this system for configuring the network after the install quite some time ago, and I wanted to do the same thing with this new kickstart box for RH/CentOS.

I noticed in initial testing that anything I was trying to output to the terminal in the ''%post'' section of the kickstart file was not showing up, but that I was able to read from the terminal.  After doing a little searching, I found [[http://hintshop.ludvig.co.nz/show/interactive-pre-post-install-scripts-redhat-kickstart/|this post]] that gave me the jumpstart I needed to get this all straightened out.  The problem I had was that though the example would work just fine for when we are standing at the machine with a crash cart, I also had configs set up to do the installs over a serial console.  That example just wouldn't work for that situation.

For the purposes of brevity, I'm going to assume you are already familiar with the kickstart system, have a server, etc.  I'm just going to cover the interactive input in the ''%post'' section of the kickstart file.

===== %post =====
I'm not going to waste much time here, but just jump in and get to the code.

<code bash>
%post
hostname=""
ip=""
netmask=""
gw=""
opts=""
answer="n"
device="eth0"
hwaddr=`ifconfig $device | grep -i hwaddr | sed -e 's#^.*hwaddr[[:space:]]*##I'`
dns1="205.171.2.65"
dns2="205.171.3.65"

curTTY=`tty`
exec < $curTTY > $curTTY 2> $curTTY
clear

while [ x"$answer" != "xy" ] && [ x"$answer" != "xY" ] ; do
        echo -n "enter hostname: "; read hostname
        echo -n "enter ip: "; read ip
        echo -n "enter netmask: "; read netmask
        echo -n "enter default gw: "; read gw
        echo -n "hard set '100baseTX full-dulplex' [y/n] " ; read opts
        echo

        echo You entered:
        echo -e "\thostname: $hostname"
        echo -e "\tip: $ip"
        echo -e "\tnetmask: $netmask"
        echo -e "\tdefault gw: $gw"
        echo -e "\tset 100baseTX full-duplex: $opts"
        echo -n "Is this correct? [y/n] "; read answer
done

if [ x"$opts" = "xy" ] ; then
        opts="speed 100 duplex full autoneg off"
else
        opts=""
fi

sed -i -e 's#^\(HOSTNAME=\).*$#\1'"$hostname"'#' /etc/sysconfig/network
echo GATEWAY=$gw >> /etc/sysconfig/network

echo DEVICE=$device > $scrFile
echo BOOTPROTO=static >> $scrFile
echo ONBOOT=yes >> $scrFile
echo NM_CONTROLLED=no >> $scrFile
echo HWADDR=$hwaddr >> $scrFile
echo IPADDR=$ip >> $scrFile
echo NETMASK=$netmask >> $scrFile
echo USERCTL=no >> $scrFile
echo DNS1=$dns1 >> $scrFile
echo DNS2=$dns2 >> $scrFile

if [ "x$opts" != "x" ] ; then
        echo 'ETHTOOL_OPTS="'"$opts"'"' >> $scrFile
fi


%end
</code>

As you can see, there's nothing really fancy about this simple shell based menu (which you can definitely expand upon).  The real points of interest here are in these lines:

<code bash>
curTTY=`tty`
exec < $curTTY > $curTTY 2> $curTTY
clear
</code>

First, we are setting the ''curTTY'' variable to what our current terminal is.  In the next line we are explicitly setting this scripts I/O to the tty's standard descriptors.  And finally, in the 3rd line, we just clear the terminal window for a fresh start.

This is really where we end up with a better solution than the example I originally found since we are using our current tty, whatever it is, to interact with you.

I hope this helps someone else out in the future.  As I mentioned at the beginning of this article, I will also be writing a full tutorial on setting up a kickstart PXE server soon.