vzdump: drop overly scary & outdated warning about fleecing

[pve-docs.git] / vzdump.adoc

[[chapter_vzdump]]
ifdef::manvolnum[]
vzdump(1)
=========
:pve-toplevel:

NAME
----

vzdump - Backup Utility for VMs and Containers 


SYNOPSIS
--------

include::vzdump.1-synopsis.adoc[]


DESCRIPTION
-----------
endif::manvolnum[]
ifndef::manvolnum[]
Backup and Restore
==================
:pve-toplevel:
endif::manvolnum[]

Backups are a requirement for any sensible IT deployment, and {pve}
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.

{pve} 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 short 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 started, the VM goes to full
operation mode if it was previously running. Consistency is guaranteed
by using the live backup feature.

`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 inconsistency risk. It works by performing a {pve} 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 {pve} live backup for QemuServer can
be found online
https://git.proxmox.com/?p=pve-qemu.git;a=blob_plain;f=backup.txt[here].

NOTE: {pve} live backup provides snapshot-like semantics on any
storage type. It does not require that the underlying storage supports
snapshots. Also please note that since the backups are done via 
a background Qemu process, a stopped VM will appear as running for a 
short amount of time while the VM disks are being read by Qemu.
However the VM itself is not booted, only its disk(s) are read.

.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/CIFS 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).

// see PVE::VZDump::LXC::prepare()
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 {pve} 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.

Backup File Compression
-----------------------

The backup file can be compressed with one of the following algorithms: `lzo`
footnote:[Lempel–Ziv–Oberhumer a lossless data compression algorithm
https://en.wikipedia.org/wiki/Lempel-Ziv-Oberhumer], `gzip` footnote:[gzip -
based on the DEFLATE algorithm https://en.wikipedia.org/wiki/Gzip] or `zstd`
footnote:[Zstandard a lossless data compression algorithm
https://en.wikipedia.org/wiki/Zstandard].

Currently, Zstandard (zstd) is the fastest of these three algorithms.
Multi-threading is another advantage of zstd over lzo and gzip. Lzo and gzip
are more widely used and often installed by default.

You can install pigz footnote:[pigz - parallel implementation of gzip
https://zlib.net/pigz/] as a drop-in replacement for gzip to provide better
performance due to multi-threading. For pigz & zstd, the amount of
threads/cores can be adjusted. See the
xref:vzdump_configuration[configuration options] below.

The extension of the backup file name can usually be used to determine which
compression algorithm has been used to create the backup.

|===
|.zst | Zstandard (zstd) compression
|.gz or .tgz | gzip compression
|.lzo | lzo compression
|===

If the backup file name doesn't end with one of the above file extensions, then
it was not compressed by vzdump.


[[vzdump_restore]]
Restore
-------

A backup archive can be restored through the {pve} 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.

Bandwidth Limit
~~~~~~~~~~~~~~~

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. {pve}
implements two kinds of limits for restoring and archive:

* per-restore limit: denotes the maximal amount of bandwidth for
  reading from a backup archive

* per-storage write limit: denotes the maximal amount of bandwidth used for
  writing to a specific storage

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.

NOTE: You can use `0` for the `bwlimit` parameter to disable all limits for
a specific restore job. This can be helpful if you need to restore a very
important virtual guest as fast as possible. (Needs `Data.Allocate'
permissions on storage)

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
----

[[vzdump_configuration]]
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:

include::vzdump.conf.5-opts.adoc[]


.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 -


ifdef::manvolnum[]
include::pve-copyright.adoc[]
endif::manvolnum[]