11.2. Création de modèles de machines virtuelles
To create multiple virtual machine (VM) clones that work correctly, you can remove information and configurations that are unique to a source VM, such as SSH keys or persistent network MAC configuration. This creates a VM template, which you can use to easily and safely create VM clones.
You can create VM templates using the virt-sysprep utility or you can create them manually based on your requirements.
11.2.1. Creating a virtual machine template using virt-sysprep
To create a cloning template from an existing virtual machine (VM), you can use the virt-sysprep utility. This removes certain configurations that might cause the clone to work incorrectly, such as specific network settings or system registration metadata. As a result, virt-sysprep makes creating clones of the VM more efficient, and ensures that the clones work more reliably.
Conditions préalables
The
guestfs-toolspackage, which contains thevirt-syspreputility, is installed on your host:# dnf install guestfs-tools- The source VM intended as a template is shut down.
You know where the disk image for the source VM is located, and you are the owner of the VM’s disk image file.
Note that disk images for VMs created in the system connection of libvirt are located in the
/var/lib/libvirt/imagesdirectory and owned by the root user by default:# ls -la /var/lib/libvirt/images -rw-------. 1 root root 9665380352 Jul 23 14:50 a-really-important-vm.qcow2 -rw-------. 1 root root 8591507456 Jul 26 2017 an-actual-vm-that-i-use.qcow2 -rw-------. 1 root root 8591507456 Jul 26 2017 totally-not-a-fake-vm.qcow2 -rw-------. 1 root root 10739318784 Sep 20 17:57 another-vm-example.qcow2- Optional: Any important data on the source VM’s disk has been backed up. If you want to preserve the source VM intact, clone it first and turn the clone into a template.
Procédure
Ensure you are logged in as the owner of the VM’s disk image:
# whoami rootOptional: Copy the disk image of the VM.
# cp /var/lib/libvirt/images/a-really-important-vm.qcow2 /var/lib/libvirt/images/a-really-important-vm-original.qcow2This is used later to verify that the VM was successfully turned into a template.
Use the following command, and replace /var/lib/libvirt/images/a-really-important-vm.qcow2 with the path to the disk image of the source VM.
# virt-sysprep -a /var/lib/libvirt/images/a-really-important-vm.qcow2 [ 0.0] Examining the guest ... [ 7.3] Performing "abrt-data" ... [ 7.3] Performing "backup-files" ... [ 9.6] Performing "bash-history" ... [ 9.6] Performing "blkid-tab" ... [...]
Vérification
To confirm that the process was successful, compare the modified disk image to the original one. The following example shows a successful creation of a template:
# virt-diff -a /var/lib/libvirt/images/a-really-important-vm-orig.qcow2 -A /var/lib/libvirt/images/a-really-important-vm.qcow2 - - 0644 1001 /etc/group- - - 0000 797 /etc/gshadow- = - 0444 33 /etc/machine-id [...] - - 0600 409 /home/username/.bash_history - d 0700 6 /home/username/.ssh - - 0600 868 /root/.bash_history [...]
Ressources supplémentaires
-
The OPERATIONS section in the
virt-sysprepman page - Cloning a virtual machine using the command-line interface
11.2.2. Creating a virtual machine template manually
To create a template from an existing virtual machine (VM), you can manually reset or unconfigure a guest VM to prepare it for cloning.
Conditions préalables
Ensure that you know the location of the disk image for the source VM and are the owner of the VM’s disk image file.
Note that disk images for VMs created in the system connection of libvirt are by default located in the
/var/lib/libvirt/imagesdirectory and owned by the root user:# ls -la /var/lib/libvirt/images -rw-------. 1 root root 9665380352 Jul 23 14:50 a-really-important-vm.qcow2 -rw-------. 1 root root 8591507456 Jul 26 2017 an-actual-vm-that-i-use.qcow2 -rw-------. 1 root root 8591507456 Jul 26 2017 totally-not-a-fake-vm.qcow2 -rw-------. 1 root root 10739318784 Sep 20 17:57 another-vm-example.qcow2- Ensure that the VM is shut down.
- Optional: Any important data on the VM’s disk has been backed up. If you want to preserve the source VM intact, clone it first and edit the clone to create a template.
Procédure
Configure the VM for cloning:
- Install any software needed on the clone.
- Configure any non-unique settings for the operating system.
- Configure any non-unique application settings.
Remove the network configuration:
Remove any persistent udev rules using the following command:
# rm -f /etc/udev/rules.d/70-persistent-net.rulesNoteIf udev rules are not removed, the name of the first NIC might be
eth1instead ofeth0.Remove unique network details from ifcfg scripts by editing
/etc/sysconfig/network-scripts/ifcfg-eth[x]as follows:Remove the HWADDR and Static lines:
NoteIf the HWADDR does not match the new guest’s MAC address, the
ifcfgwill be ignored.DEVICE=eth[x] BOOTPROTO=none ONBOOT=yes #NETWORK=10.0.1.0 <- REMOVE #NETMASK=255.255.255.0 <- REMOVE #IPADDR=10.0.1.20 <- REMOVE #HWADDR=xx:xx:xx:xx:xx <- REMOVE #USERCTL=no <- REMOVE # Remove any other *unique or non-desired settings, such as UUID.*Configure DHCP but do not include HWADDR or any other unique information:
DEVICE=eth[x] BOOTPROTO=dhcp ONBOOT=yes
Ensure the following files also contain the same content, if they exist on your system:
-
/etc/sysconfig/networking/devices/ifcfg-eth[x] /etc/sysconfig/networking/profiles/default/ifcfg-eth[x]NoteIf you had used
NetworkManageror any special settings with the VM, ensure that any additional unique information is removed from theifcfgscripts.
-
Remove registration details:
For VMs registered on the Red Hat Network (RHN):
# rm /etc/sysconfig/rhn/systemidFor VMs registered with Red Hat Subscription Manager (RHSM):
If you do not plan to use the original VM:
# subscription-manager unsubscribe --all # subscription-manager unregister # subscription-manager cleanIf you plan to use the original VM:
# subscription-manager cleanNoteThe original RHSM profile remains in the Portal along with your ID code. Use the following command to reactivate your RHSM registration on the VM after it is cloned:
#subscription-manager register --consumerid=71rd64fx-6216-4409-bf3a-e4b7c7bd8ac9
Remove other unique details:
Remove ssh public/private key pairs:
# rm -rf /etc/ssh/ssh_host_exampleRemove the configuration of LVM devices:
# rm /etc/lvm/devices/system.devices- Remove any other application-specific identifiers or configurations that might cause conflicts if running on multiple machines.
Remove the
gnome-initial-setup-donefile to configure the VM to run the configuration wizard on the next boot:# rm ~/.config/gnome-initial-setup-doneNoteThe wizard that runs on the next boot depends on the configurations that have been removed from the VM. In addition, on the first boot of the clone, it is recommended that you change the hostname.
