General Information

After installing an OS via kickstart or a VM Template, there is typically additional standard configuration performed depending upon the environment.

Checklist

• Distro(s): Enterprise Linux 6/7
• Other: NFS Server sharing a post install configuration script

Post install configuration is normally only needed to be completed the first time a system is booted in order to set it up for the type of environment it is in.

This script is meant to run once and then disable itself. It calls other post install script(s) to do the actual work.

#!/bin/bash
# Name: firstboot.sh
# Description: Auto runs a post install script 1 time
 
#### Customize These Variables ####
nfs_server="10.1.2.3"
nfs_server_share="${nfs_server}:/scripts"
nfs_client_mountpoint="/mnt"
post_install_script="${nfs_client_mountpoint}/scripts/postinstall.sh"
 
# Write a successful run file
firstboot_ran_file="/root/.firstboot-ran"
 
# Reboot delay in minutes
reboot_delay="1"
#### End of Customize Variables ####
 
#==============================
# Functions; Main Starts After
#==============================
function check_os_type
{
## Gather Distro and Major Version
  if [ -f /etc/system-release-cpe ];then
    distro=$(awk -F: '{printf "%s", $3}' /etc/system-release-cpe)
    major_version=$(awk -F: '{printf "%d", $5}' /etc/system-release-cpe)
  elif [ -f /etc/redhat-release ];then
    distro=$(awk '{printf "%s", $1}' /etc/redhat-release)
    major_version=$(awk -F. '{print $1}' /etc/redhat-release | awk '{printf "%d", $3}')
  fi
}
 
#====================
# Main Program
#====================
 
echo -e "================================================"
echo -e "####========== Firstboot Script ============####"
echo -e "================================================"
 
# Check to see if script has been run before
if [[ -f ${firstboot_ran_file} ]]; then
  echo -e "\nfirstboot>> Error; First boot ran file detected at: ${firstboot_ran_file}!"
  echo -e "firstboot>> Will NOT execute this script. If you really want to execute, remove that file."
  exit 1
fi
 
# Discover OS Type
check_os_type
 
# Start rpcbind service
if [[ ${major_version} == "7" ]]; then
  systemctl start rpcbind
else
  service rpcbind start
fi
 
# Try to reach the NFS server 3 times
for index in 1 2 3; do
  ping -c 1 ${nfs_server} &> /dev/null
 
  if [[ $? -eq 0 ]]; then
    # Successful ping, exit loop
    break
  else
    # Unsuccessful; wait 10 seconds and try again
    echo -e "firstboot>> Could not reach ${nfs_server}. Sleeping for 10 seconds and will try again."
    sleep 10
  fi
done
 
# Mount script location
echo -e "\nfirstboot>> Mounting script location..."
mount -t nfs ${nfs_server_share} ${nfs_client_mountpoint}
 
# Execute post install script
echo -e "\nfirstboot>> Executing post install script..."
${post_install_script}
 
if [[ $? -eq 0 ]]; then
  echo -e "\nfirstboot>> Post install script successful."
else
  echo -e "\nfirstboot>> Error; Post install script exited with error(s)! Quiting..."
  exit 1
fi
 
#==============================================
# Call other post install scripts/actions here
#==============================================
 
# Unmount nfs share
echo -e "\nfirstboot>> Unmounting nfs share.."
umount ${nfs_client_mountpoint}
 
#### Safeguards to prevent firstboot.sh from running more than once ####
# Create firstboot-ran file
echo -e "\nfirstboot>> Creating firstboot ran file..."
echo -e "firstboot>> firstboot.sh was run on $(date)." > ${firstboot_ran_file}
chown -v root:root ${firstboot_ran_file}
chmod -v 400 ${firstboot_ran_file}
 
# Make script not executable
echo -e "\nfirstboot>> Removing execute permissions on this script..."
chown -v root:root ${0}
chmod -v 400 ${0}
 
# Disable auto execution
if [[ ${major_version} == "7" ]]; then
  systemctl disable firstboot.service
else
  sed -i '/firstboot.sh/d' /etc/rc.d/rc.local
fi
#### End of Safeguards ####
 
# Email root notification of completion
echo -e "\nfirstboot>> E-mailing root notification that the script completed..."
echo -e "The firstboot script process has completed for: '$(hostname)' on $(date).\n\nThe following actions have successfully run:\n1) Post install script (System updates, General system configuration)\n2) Other scripts\n\nThe system ($(hostname)) will reboot in ${reboot_delay} minute(s)." | /bin/mail -s "Firstboot Complete: $(hostname)" root
 
# Allow some time for the email to be sent
sleep 5
 
# Reboot system
shutdown -r +${reboot_delay} "firstboot>> Post install script(s) complete. System will be rebooted."

Firstboot will get executed on CentOS 7 via a custom systemd service unit.

The following service unit will end up in /etc/systemd/system/firstboot.service

[Unit]
Description=Auto-execute post install scripts
After=network.target
 
[Service]
ExecStart=/root/scripts/firstboot.sh
 
[Install]
WantedBy=multi-user.target

CentOS 6 will make use of rc.local to execute the script.

/etc/rc.d/rc.local (append)

/root/scripts/firstboot.sh

Now that we have a firstboot script and method of executing on boot(CentOS 7 service or CentOS 6 rc.local), the combination of the two can be added to VM templates or kickstarts for unattended execution.

The modifications for auto execution need to be done on a new template that is a modification of your base VM Template.

Warning: Do not delete your base template after you have created an auto setup version! If you ever want to update your auto setup template, you will need to deploy from the base template, make changes, and create a new auto setup version.

• Deploy a new VM from your base template (Create a base template here)
• Make the following modifications to the new system.
  • CentOS 6

    ## VM deployed from the base template ##
     
    ## Create a script directory for root
    mkdir /root/scripts
     
    ## Mount NFS Server and Copy firstboot.sh to the VM
    mount -t nfs <nfs-server>:/scripts /mnt
    cp -v /mnt/firstboot.sh /root/scripts/
    chown -Rv root:root /root/scripts
    chmod -Rv 700 /root/scripts
     
    ## Create line in rc.local to auto execute firstboot script
    echo "/root/scripts/firstboot.sh" >> /etc/rc.d/rc.local
     
    ## Unmount NFS server
    umount /mnt

    • Run CentOS 6 clean up commands identical to the base template and create a new template.
  • CentOS 7

    ## VM deployed from the base template ##
     
    ## Create a script directory for root
    mkdir /root/scripts
     
    ## Mount NFS Server and Copy firstboot.sh to the VM
    mount -t nfs <nfs-server>:/scripts /mnt
    cp -v /mnt/firstboot.sh /root/scripts/
    chown -Rv root:root /root/scripts
    chmod -Rv 700 /root/scripts
     
    ## Copy firstboot.service unit to the VM
    cp -v /mnt/firstboot.service /etc/systemd/system/
    chown -v root:root /etc/systemd/system/firstboot.service
    chmod -v 644 /etc/systemd/system/firstboot.service
    systemctl enable firstboot.service
     
    ## Unmount NFS server
    umount /mnt

    • Run CentOS 7 clean up commands identical to the base template and create a new template.