Backup and Restore

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Backups are a requirements for any sensible IT deployment, and Proxmox VE provides a fully integrated solution, using the capabilities of each storage and each guest system type. This allows the system administrator to fine tune via the mode option between consistency of the backups and downtime of the guest system.

Proxmox VE backups are always full backups - containing the VM/CT configuration and all data. Backups can be started via the GUI or via the vzdump command line tool.

Backup Storage

Before a backup can run, a backup storage must be defined. Refer to the Storage documentation on how to add a storage. A backup storage must be a file level storage, as backups are stored as regular files. In most situations, using a NFS server is a good way to store backups. You can save those backups later to a tape drive, for off-site archiving.

Scheduled Backup

Backup jobs can be scheduled so that they are executed automatically on specific days and times, for selectable nodes and guest systems. Configuration of scheduled backups is done at the Datacenter level in the GUI, which will generate a cron entry in /etc/cron.d/vzdump.

Backup modes

There are several ways to provide consistency (option mode), depending on the guest type.

Backup modes for VMs:
stop mode

This mode provides the highest consistency of the backup, at the cost of a downtime in the VM operation. It works by executing an orderly shutdown of the VM, and then runs a background Qemu process to backup the VM data. After the backup is complete, the Qemu process resumes the VM to full operation mode if it was previously running.

suspend mode

This mode is provided for compatibility reason, and suspends the VM before calling the snapshot mode. Since suspending the VM results in a longer downtime and does not necessarily improve the data consistency, the use of the snapshot mode is recommended instead.

snapshot mode

This mode provides the lowest operation downtime, at the cost of a small inconstancy risk. It works by performing a Proxmox VE live backup, in which data blocks are copied while the VM is running. If the guest agent is enabled (agent: 1) and running, it calls guest-fsfreeze-freeze and guest-fsfreeze-thaw to improve consistency.

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

Note Proxmox VE live backup provides snapshot-like semantics on any storage type. It does not require that the underlying storage supports snapshots.
Backup modes for Containers:
stop mode

Stop the container for the duration of the backup. This potentially results in a very long downtime.

suspend mode

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

When the container is on a local file system and the target storage of the backup is an NFS server, you should set --tmpdir to reside on a local file system too, as this will result in a many fold performance improvement. Use of a local tmpdir is also required if you want to backup a local container using ACLs in suspend mode if the backup storage is an NFS server.

snapshot mode

This mode uses the snapshotting facilities of the underlying storage. First, the container will be suspended to ensure data consistency. A temporary snapshot of the container’s volumes will be made and the snapshot content will be archived in a tar file. Finally, the temporary snapshot is deleted again.

Note snapshot mode requires that all backed up volumes are on a storage that supports snapshots. Using the backup=no mount point option individual volumes can be excluded from the backup (and thus this requirement).
Note By default additional mount points besides the Root Disk mount point are not included in backups. For volume mount points you can set the Backup option to include the mount point in the backup. Device and bind mounts are never backed up as their content is managed outside the Proxmox VE storage library.

Backup File Names

Newer versions of vzdump encode the guest 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. The file uses a simple colon separated key/value format. Each line has the following format:

OPTION: value

Blank lines in the file are ignored, and lines starting with a # character are treated as comments and are also ignored. Values from this file are used as default, and can be overwritten on the command line.

We currently support the following options:

bwlimit: <integer> (0 - N) (default = 0)

Limit I/O bandwidth (KBytes per second).

compress: <0 | 1 | gzip | lzo> (default = 0)

Compress dump file.

dumpdir: <string>

Store resulting files to specified directory.

exclude-path: <string>

Exclude certain files/directories (shell globs).

ionice: <integer> (0 - 8) (default = 7)

Set CFQ ionice priority.

lockwait: <integer> (0 - N) (default = 180)

Maximal time to wait for the global lock (minutes).

mailnotification: <always | failure> (default = always)

Specify when to send an email

mailto: <string>

Comma-separated list of email addresses that should receive email notifications.

maxfiles: <integer> (1 - N) (default = 1)

Maximal number of backup files per guest system.

mode: <snapshot | stop | suspend> (default = snapshot)

Backup mode.

pigz: <integer> (default = 0)

Use pigz instead of gzip when N>0. N=1 uses half of cores, N>1 uses N as thread count.

remove: <boolean> (default = 1)

Remove old backup files if there are more than maxfiles backup files.

script: <string>

Use specified hook script.

stdexcludes: <boolean> (default = 1)

Exclude temporary files and logs.

stopwait: <integer> (0 - N) (default = 10)

Maximal time to wait until a guest system is stopped (minutes).

storage: <string>

Store resulting file to this storage.

tmpdir: <string>

Store temporary files to specified directory.

Example vzdump.conf Configuration
tmpdir: /mnt/fast_local_disk
storage: my_backup_storage
mode: snapshot
bwlimit: 10000

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

Note this option is only available for container backups.

vzdump skips the following files by default (disable with the option --stdexcludes 0)

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

You can also manually specify (additional) 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 (in ./etc/vzdump/) and will be correctly restored.

Examples

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

# vzdump 777

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

# vzdump 777 --mode suspend

Backup all guest systems and send notification mails to root and admin.

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

Use snapshot mode (no downtime) and non-default dump directory.

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

Backup more than one guest (selectively)

# vzdump 101 102 103 --mailto root

Backup all guests excluding 101 and 102

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

Restore a container to a new CT 600

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

Restore a QemuServer VM 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 -