CentOS 7 1511 Minimal oVirt Template - rharmonson/richtech GitHub Wiki

CentOS 7 1511 Minimal oVirt Template

Revised: November 16, 2016; add 'yum clean all' to sealvm.sh

Revised: November 12, 2016; added sealvm.sh & update cloud-init

Revised: October 18, 2016; clarified 'sys-unconfig'

Revised: August 15, 2016

The purpose of this article is to describe the process to create a CentOS 7 1511 Minimal oVirt virtual machine for cloning to a template.

Complete you base installation and configuration before completing the tasks described in this article. My base installation guide for CentOS 7 1511 can be found here:

https://github.com/rharmonson/richtech/wiki/CentOS-7-1511-Minimal-x86_64-Base-Installation-Guide

Process

  1. Update hostname
  2. Clear machine-id; deletion is problematic next boot
  3. Delete SSH host keys
  4. Replace ifcfg-eth0 PREFIX with NETMASK
  5. Edit ifcfg-eth0 to remove unnecessary values including HWADD
  6. Delete logs
  7. Install ovirt-guest-agent-common
  8. Complete any additional desired configurations or installations.
  9. (Install cloud-init; optional)
  10. sys-unconfig (clears host specific information then poweroff)
  11. Convert virtual machine to template
  12. Deploy virtual machine using template

Execute

Update the hostname to something generic (optional)

[root@centos7 ~]# hostnamectl set-hostname localhost.localdomain
[root@centos7 ~]# hostnamectl
   Static hostname: localhost.localdomain
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 7c84b8bda6e941f1ba4f6eb552ec8659
           Boot ID: f17bc3fb1b524cf18d4cfd22686281a2
    Virtualization: kvm
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-327.28.2.el7.x86_64
      Architecture: x86-64

Clear the machine-id.

[root@centos7 ~]# > /etc/machine-id

Clear host SSH keys and /root/.

[root@centos7 ~]# rm -f /etc/ssh/ssh_host_*
[root@centos7 ~]# rm -rf /root/.ssh/
[root@centos7 ~]# rm -f /root/anaconda-ks.cfg
[root@centos7 ~]# rm -f /root/.bash_history
[root@centos7 ~]# unset HISTFILE

Network Interface

Remove the HWADDR= line from /etc/sysconfig/network-scripts/ifcfg-eth0. Note that oVirt using cloud-init does not support PREFIX so update the ifcfg to use the equivalent NETMASK. If using static, I remove all items except, TYPE, BOOTPROTO, DEVICE, ONBOOT, IPADDR, NETMASK, and GATEWAY. Altenatively, use DHCP which result with:

TYPE=Ethernet
DEVICE=eth0
ONBOOT=yes
BOOTPROTO=dhcp

Clear logs

rm -f /var/log/boot.log
rm -f /var/log/cron
rm -f /var/log/dmesg
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/ovirt-guest-agent/ovirt-guest-agent.log
rm -f /var/log/tuned/tuned.log

Install oVirt repository, install ovirt agent, and enable it.

[root@centos7 ~]# yum install -y http://resources.ovirt.org/pub/yum-repo/ovirt-release36.rpm
[root@centos7 ~]# yum install ovirt-guest-agent-common
[root@centos7 ~]# systemctl enable ovirt-guest-agent

Cloud Init (OPTIONAL)

Install cloud-init package if desired. I experimented with cloud-init. I had mixed results for Fedora but for CentOS 7.2.1511, it worked beautifully. Remember to enable the service as shown below. Also, I suspect DHCP is a dependency but not taken the time to test.

[root@centos7 ~]# yum install cloud-init
[root@centos7 ~]# systemctl enable cloud-init

Flag as unconfigured (and poweroff).

[root@centos7 ~]# sys-unconfig

Ready to create template!

Seal Script

Peridocially, I update the templates with updates and configuration changes. I use a script to reseal the virtual machine, sealvm.sh.

yum clean all
> /etc/machine-id
rm -f /etc/ssh/ssh_host
rm -rf /root/.ssh/
rm -f /root/anaconda-ks.cfg
rm -f /root/.bash_history
unset HISTFILE
rm -f /var/log/boot.log
rm -f /var/log/cron
rm -f /var/log/dmesg
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/ovirt-guest-agent/ovirt-guest-agent.log
rm -f /var/log/tuned/tuned.log
sys-unconfig

References