Creating a new KVM virtual machine from a template
If you've seen the blog post about creating a template for KVM virtual machines then you probably were wondering how to actually clone an already existing template system.
Well, this blog post is exactly about this - how you can clone an existing KVM template system and spawn new instances.
Login to the hypervisor
Create a logical volume first for the new virtual machine.
Below is an example command which creates a new LVM volume called www-proxy, from the vg0 volume group, which we'll use to install the Varnish HTTP Accelerator.
$ sudo lvcreate -L10G -n www-proxy vg0
Next we clone the system from an existing template.
Below is an example command which creates the www-proxy virtual machine using the debian-squeeze template system:
$ sudo virt-clone --original debian-squeeze --name www-proxy --file /dev/mapper/vg0-www-proxy
Wait for the clone to be completed and then proceed to the next steps.
First, we need to start up the newly created machine and perform some post-clone actions.
Login to the hypervisor and start up the new system.
$ sudo virsh virsh# start www-proxy
You can watch the system booting by executing the
Once the system boots up, login to it and do the post-clone steps listed below.
- Update /etc/hosts
- Update network interfaces
- Set hostname
- Create ssh keys for the host
For creating the server's SSH keys execute the commands below:
$ sudo ssh-keygen -t rsa -f /etc/ssh/ssh_host_rsa_key $ sudo ssh-keygen -t dsa -f /etc/ssh/ssh_host_dsa_key $ sudo ssh-keygen -t ecdsa -f /etc/ssh/ssh_host_ecdsa_key
- Create the atjobs directory needed for running atd(8):
This is needed because during the preparation of the template system (via virt-sysprep(8)) the atjobs directory is being removed.
$ sudo mkdir /var/spool/cron/atjobs
- Create the /var/log/wtmp file to store login information
To create the file, simply touch(1) it:
$ sudo touch /var/log/wtmp
One last thing that remains to be done is to autostart the system during boot-time. To do that, execute the command below from the virsh(1) console:
virsh# autostart www-proxy
Once ready, reboot the system and you are good to go.