16.6. Restore

A backup archive can be restored through the Proxmox VE web GUI or through the following CLI tools:

pct restore
Container restore utility
qmrestore
Virtual Machine restore utility

For details see the corresponding manual pages.

Restoring one or more big backups may need a lot of resources, especially storage bandwidth for both reading from the backup storage and writing to the target storage. This can negatively affect other virtual guests as access to storage can get congested.

To avoid this you can set bandwidth limits for a backup job. Proxmox VE implements two kinds of limits for restoring and archive:

The read limit indirectly affects the write limit, as we cannot write more than we read. A smaller per-job limit will overwrite a bigger per-storage limit. A bigger per-job limit will only overwrite the per-storage limit if you have ‘Data.Allocate’ permissions on the affected storage.

You can use the ‘--bwlimit <integer>` option from the restore CLI commands to set up a restore job specific bandwidth limit. Kibit/s is used as unit for the limit, this means passing `10240’ will limit the read speed of the backup to 10 MiB/s, ensuring that the rest of the possible storage bandwidth is available for the already running virtual guests, and thus the backup does not impact their operations.

Most times your storage’s generally available bandwidth stays the same over time, thus we implemented the possibility to set a default bandwidth limit per configured storage, this can be done with:

# pvesm set STORAGEID --bwlimit restore=KIBs

Restoring a large backup can take a long time, in which a guest is still unavailable. For VM backups stored on a Proxmox Backup Server, this wait time can be mitigated using the live-restore option.

Enabling live-restore via either the checkbox in the GUI or the --live-restore argument of qmrestore causes the VM to start as soon as the restore begins. Data is copied in the background, prioritizing chunks that the VM is actively accessing.

Note that this comes with two caveats:

This mode of operation is especially useful for large VMs, where only a small amount of data is required for initial operation, e.g. web servers - once the OS and necessary services have been started, the VM is operational, while the background task continues copying seldom used data.

The File Restore button in the Backups tab of the storage GUI can be used to open a file browser directly on the data contained in a backup. This feature is only available for backups on a Proxmox Backup Server.

For containers, the first layer of the file tree shows all included pxar archives, which can be opened and browsed freely. For VMs, the first layer shows contained drive images, which can be opened to reveal a list of supported storage technologies found on the drive. In the most basic case, this will be an entry called part, representing a partition table, which contains entries for each partition found on the drive. Note that for VMs, not all data might be accessible (unsupported guest file systems, storage technologies, etc…).

Files and directories can be downloaded using the Download button, the latter being compressed into a zip archive on the fly.

To enable secure access to VM images, which might contain untrusted data, a temporary VM (not visible as a guest) is started. This does not mean that data downloaded from such an archive is inherently safe, but it avoids exposing the hypervisor system to danger. The VM will stop itself after a timeout. This entire process happens transparently from a user’s point of view.