What does the positional parameters of "virsh backup-begin" actually do?
Normally when I backup a kvm machine I shutdown the machine then run: virsh list -all virsh shutdown Ubuntu18 virsh dumpxml Ubuntu18 > /MyBackup/Ubuntu18.xml cp /var/lib/libvirt/images/Ubuntu18.qcow2 /MyBackup/Ubuntu18.qcow2 However, I found a new sub-command. The help file says: % virsh backup-begin --help NAME backup-begin - Start a disk backup of a live domain SYNOPSIS backup-begin <domain> [--backupxml <string>] [--checkpointxml <string>] [--reuse-external] DESCRIPTION Use XML to start a full or incremental disk backup of a live domain, optionally creating a checkpoint OPTIONS [--domain] <string> domain name, id or uuid --backupxml <string> domain backup XML --checkpointxml <string> domain checkpoint XML --reuse-external reuse files provided by caller The problem with this help is, it is not clear enough. I understand that I should use virsh backup-begin vm1 to backup a live kvm machine. However, this command only create .qcow2 files. What about the .xml file. What does --backupxml , --checkpointxml & --reuse-external actually do? When should I use them?
On Fri, Jan 14, 2022 at 23:39:10 +0600, Ahmad Ismail wrote:
Normally when I backup a kvm machine I shutdown the machine then run:
[...]
The problem with this help is, it is not clear enough.
I understand that I should use virsh backup-begin vm1 to backup a live kvm machine. However, this command only create .qcow2 files. What about the .xml file.
What does --backupxml , --checkpointxml & --reuse-external actually do?
When should I use them?
'man virsh' states: backup-begin Syntax: backup-begin domain [backupxml] [checkpointxml] [--reuse-external] Begin a new backup job. If backupxml is omitted, this defaults to a full backup using a push model to filenames generated by lib‐ virt; supplying XML allows fine-tuning such as requesting an in‐ cremental backup relative to an earlier checkpoint, controlling which disks participate or which filenames are involved, or re‐ questing the use of a pull model backup. The backup-dumpxml com‐ mand shows any resulting values assigned by libvirt. For more in‐ formation on backup XML, see: https://libvirt.org/formatbackup.html If --reuse-external is used it instructs libvirt to reuse tempo‐ rary and output files provided by the user in backupxml. If checkpointxml is specified, a second file with a top-level ele‐ ment of domaincheckpoint is used to create a simultaneous check‐ point, for doing a later incremental backup relative to the time the backup was created. See checkpoint-create for more details on checkpoints. This command returns as soon as possible, and the backup job runs in the background; the progress of a push model backup can be checked with domjobinfo or by waiting for an event with event (the progress of a pull model backup is under the control of whatever third party connects to the NBD export). The job is ended with domjobabort. Does this clarify it sufficiently?
Understood everything except or by waiting for an event with event (the progress of a pull model backup
is under the control of whatever third party connects to the NBD export)
How do I wait for an event with event. Can you please give an example. However, the clarification till now is sufficient for me. Specially the link was very helpful. One more thing, There are some documents which say: backup-begin <domain> [--backupxml <string>] [--checkpointxml <string>] [--reuse-external] There are others which say: backup-begin domain [backupxml] [checkpointxml] [--reuse-external] Which syntax is right? On Sat, Jan 15, 2022 at 3:19 AM Peter Krempa <pkrempa@redhat.com> wrote:
On Fri, Jan 14, 2022 at 23:39:10 +0600, Ahmad Ismail wrote:
Normally when I backup a kvm machine I shutdown the machine then run:
[...]
The problem with this help is, it is not clear enough.
I understand that I should use virsh backup-begin vm1 to backup a live kvm machine. However, this command only create .qcow2 files. What about the .xml file.
What does --backupxml , --checkpointxml & --reuse-external actually do?
When should I use them?
'man virsh' states:
backup-begin Syntax:
backup-begin domain [backupxml] [checkpointxml] [--reuse-external]
Begin a new backup job. If backupxml is omitted, this defaults to a full backup using a push model to filenames generated by lib‐ virt; supplying XML allows fine-tuning such as requesting an in‐ cremental backup relative to an earlier checkpoint, controlling which disks participate or which filenames are involved, or re‐ questing the use of a pull model backup. The backup-dumpxml com‐ mand shows any resulting values assigned by libvirt. For more in‐ formation on backup XML, see: https://libvirt.org/formatbackup.html
If --reuse-external is used it instructs libvirt to reuse tempo‐ rary and output files provided by the user in backupxml.
If checkpointxml is specified, a second file with a top-level ele‐ ment of domaincheckpoint is used to create a simultaneous check‐ point, for doing a later incremental backup relative to the time the backup was created. See checkpoint-create for more details on checkpoints.
This command returns as soon as possible, and the backup job runs in the background; the progress of a push model backup can be checked with domjobinfo or by waiting for an event with event (the progress of a pull model backup is under the control of whatever third party connects to the NBD export). The job is ended with domjobabort.
Does this clarify it sufficiently?
participants (2)
-
Ahmad Ismail -
Peter Krempa