Most of them areoutdated, but provide historical design context.
They arenotuser documentation and should not be treated as such.
Documentation is available here.
Sealing a VM Template
‘Sealing’ is an operation that erases all machine-specific configurations from a filesystem: This includes SSH keys, UDEV rules, MAC addresses, system ID, hostname, etc. It is useful for when you want to create a template from a virtual machine. Subsequent virtual machines made from this template will avoid configuration inheritance.
virt-sysprep tool is used for sealing a VM template. Sealing operates directly on a VM’s filesystem, and the list of images is passed to it in parameters. The objective is to add the ability to run
virt-sysprep from oVirt on a specified set of disk images. The best timing for this action is when a VM template is created from a VM.
The exact list of operations performed by
virt-sysprep can be found on the tool’s manual page. oVirt runs
virt-sysprep with a set of default operations. Currently,
virt-sysprep only supports Linux guests and has only been tested on major distributions.
- Name: Shmuel Melamud (smelamud)
- Email: email@example.com
In UI, ‘Seal template’ checkbox will appear in ‘New Template’ dialog. If user checks this checkbox, the VM Template will be sealed just after creation.
Disk images marked as SHARED cannot be modified. Therefore, you cannot run
AddVmTemplateCommand is finished. Sealing must be performed directly after the VM template’s disks have been created, but before the disks are marked as SHARED. Here is the correct sequence:
- Create the template.
- Create all template disks as regular (LEAF) disks.
- Make the disks ILLEGAL.
- Seal the template (run
virt-sysprepon the disks).
- Make the disks LEGAL and SHARED.
In the event of a mid-process failure, the whole process will fail and the template will be removed. If the disks are not removed after failure, they will be left ILLEGAL and unusable.
virt-sysprep utility is executed on the VDSM side. The verb is
VM.seal. The utility is executed asynchronously using host jobs mechanism. Storage jobs cannot be used for this, because
virt-sysprep operates on all disks together, and not disk-by-disk. Therefore, another type of host jobs, named ‘virt jobs’, needs to be added. The engine will track the status of the job, using
List of code changes
- Add a ‘Seal template’ checkbox to the ‘New Template’ dialog.
- Add a
sealflag to the virtual machine template creation operation.
StorageJobCallbackto be inherited from a common ancestor,
HostJobCallback, that will contain the common functionality.
UpdateVolumeCommand, to change volume flags, making it ILLEGAL, LEGAL and SHARED.
VM.sealverb on the VDSM side.
AddVmTemplateCommandso that it can perform all the steps mentioned above.
SDM.update_volumeverb that changes volume attributes.
VM.sealverb that runs
virt-sysprepon the given list of disk images.
- engine: Released
- vdsm: Released