CentOS 7: Use a live VM as template

When the need arises to create a new VM I normally clone a dedicated base machine with the common tools and configurations needed to get a new machine up and running quickly.

So every time I encounter a new application that I need in multiple future machines I install that application on the dedicated base machine.

Since the base machine is live, it gets log files, history, passwords etc., which should not be carried over to the new machine.

For this purpose, the following script has been created. The script cleans up the most common things, then unconfigures the system

#!/usr/bin/env bash

# Configuration of network interface names
NETWORK_NAME_PUBLIC="public"
NETWORK_NAME_BACKBONE="backbone"

# Make sure the user really wants to run this
read -r -p "This script will clear all local data and prepare the machine for templating. Remember to create a snapshot before running this script. Are you sure you want to continue (y/N)? " response
echo
if [[ ! $response =~ [Yy]$ ]]
then
exit 1;
fi

# Reset the hostname
echo "* Change to generic hostname"
hostnamectl set-hostname localhost.localdomain

# Reset the machine id
echo "* Resetting machine-id"
> /etc/machine-id

# Clean up temporary files created in the live base machine
echo "* Removing roots temporary files"
rm -f /etc/ssh/ssh_host_*
rm -f /root/.ssh/known_hosts*
rm -f /root/.ssh/id_*
rm -f /root/.ssh/config
rm -f /root/anaconda-ks.cfg
rm -f /root/.bash_history
rm -rf /root/.config
rm -rf /root/.cache
rm -f /root/.viminfo
unset HISTFILE

# Remove mac-addresses
echo "* Removing MAC addresses from network configurations"
sed -i '/.*HWADDR=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_PUBLIC}
sed -i '/.*UUID=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_PUBLIC}
sed -i '/.*DEVICE=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_PUBLIC}
echo "DEVICE=eth0" >> /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_PUBLIC}

sed -i '/.*HWADDR=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_BACKBONE}
sed -i '/.*UUID=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_BACKBONE}
sed -i '/.*DEVICE=.*$/d' /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_BACKBONE}
echo "DEVICE=eth1" >> /etc/sysconfig/network-scripts/ifcfg-${NETWORK_NAME_BACKBONE}

# Clear logs
echo "* Clear logs"
rm -f /var/log/boot.log
rm -f /var/log/btmp
rm -f /var/log/cron
rm -f /var/log/dmesg
rm -f /var/log/dmesg.old
rm -f /var/log/grubby
rm -f /var/log/lastlog
rm -f /var/log/maillog
rm -f /var/log/messages
rm -f /var/log/secure
rm -f /var/log/spooler
rm -f /var/log/tallylog
rm -f /var/log/wpa_supplicant.log
rm -f /var/log/wtmp
rm -f /var/log/yum.log
rm -f /var/log/audit/audit.log
rm -f /var/log/qemu-ga/*
rm -f /var/log/tuned/tuned.log

# Force a disk check on next boot
echo "* Enable fsck on next boot"
touch /forcefsck

# Run sys-unconfig
read -r -p "System is prepared, run sys-unconfig (y/N)? " response
echo
if [[ ! $response =~ [Yy]$ ]]
then
exit 1;
fi

sys-unconfig

Use this script on a cloned machine, not the live dedicated base machine since it will remove all history and reset some configurations.

Note: My machines have 2 network interfaces and their names are configured at the top in NETWORK_NAME_PUBLIC, NETWORK_NAME_BACKBONE

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