vzdump.adoc

Backup and Restore

vzdump is a utility to make consistent snapshots of running virtual machines (VMs). It basically creates an archive of the VM private area, which also includes the VM configuration files. vzdump currently supports LXC containers and QemuServer VMs.

There are several ways to provide consistency (option mode):

stop mode

Stop the VM during backup. This results in a very long downtime.

suspend mode

For containers, this mode uses rsync to copy the VM data to a temporary location (see option --tmpdir). Then the VM is suspended and a second rsync copies changed files. After that, the VM is started (resumed) again. This results in minimal downtime, but needs additional space to hold the VM copy.

For QemuServer, this mode will suspend the VM, start a live backup, and resume the VM.

snapshot mode

For containers, this mode uses the snapshotting facilities of the underlying storage. A snapshot will be made of the container volume, and the snapshot content will be archived in a tar file.

For QemuServer, this mode will do a live backup similar to the suspend mode, but without suspending/resuming the VM.

A technical overview of the Proxmox VE live backup for QemuServer can be found online here,

Backup File Names

Newer versions of vzdump encode the virtual machine type and the backup time into the filename, for example

vzdump-lxc-105-2009_10_09-11_04_43.tar

That way it is possible to store several backup in the same directory. The parameter maxfiles can be used to specify the maximum number of backups to keep.

Restore

The resulting archive files can be restored with the following programs.

pct restore

Container restore utility

qmrestore

QemuServer restore utility

For details see the corresponding manual pages.

Configuration

Global configuration is stored in /etc/vzdump.conf.

tmpdir: DIR
dumpdir: DIR
storage: STORAGE_ID
mode: snapshot|suspend|stop
bwlimit: KBPS
ionize: PRI
lockwait: MINUTES
stopwait: MINUTES
size: MB
maxfiles: N
script: FILENAME
exclude-path: PATHLIST

Hook Scripts

You can specify a hook script with option --script. This script is called at various phases of the backup process, with parameters accordingly set. You can find an example in the documentation directory (vzdump-hook-script.pl).

File Exclusions

First, this option is only available for container backups. vzdump skips the following files with option --stdexcludes

/var/log/?*
/tmp/?*
/var/tmp/?*
/var/run/?*pid

Or you can manually specify exclude paths, for example:

# vzdump 777 --exclude-path /tmp/ --exclude-path '/var/foo*'

(only excludes tmp directories)

Configuration files are also stored inside the backup archive (/etc/vzdump/), and will be correctly restored.

Examples

Simply dump VM 777 - no snapshot, just archive the VM private area and configuration files to the default dump directory (usually /var/liv//vz/dump/).

# vzdump 777

Use rsync and suspend/resume to create a snapshot (minimal downtime).

# vzdump 777 --mode suspend

Backup all VMs and send notification mails to root and admin.

# vzdump --all --mode suspend --mailto root --mailto admin

Use snapshot mode (no downtime).

# vzdump 777 --dumpdir /mnt/backup --mode snapshot

Backup more than one VM (selectively)

# vzdump 101 102 103 --mailto root

Backup all VMs excluding VM 101 and 102

# vzdump --mode suspend --exclude 101,102

Restore a container to a new VM 600

# pct restore 600 /mnt/backup/vzdump-lxc-777.tar

Restore a Qemu/KVM machine to VM 601

# qmrestore /mnt/backup/vzdump-qemu-888.vma 601

Clone an existing container 101 to a new container 300 with a 4GB root file system, using pipes

# vzdump 101 --stdout | pct restore --rootfs 4 300 -