SNAPPER(8)

Filesystem Snapshot Management

SNAPPER(8)

NAME¶

snapper - Command-line program for filesystem snapshot management

SYNOPSIS¶

snapper [--global-opts] command [--command-opts] [command-arguments]

snapper {--help}

DESCRIPTION¶

Snapper is a command-line program for filesystem snapshot management. It can create, delete and compare snapshots and undo changes done between snapshots.

Snapper never modifies the content of snapshots. Thus snapper creates read-only snapshots if supported by the kernel. Supported filesystems are btrfs and ext4 (discontinued) as well as snapshots of LVM logical volumes with thin-provisioning. Some filesystems might not be supported depending on your installation.

CONCEPTS¶

Configurations¶

For each filesystem or subvolume that should be snapshotted by snapper, a configuration file is required, see snapper-configs(5). The setup can be done with the create-config command.

Snapshots¶

Snapper distinguishes three types of snapshots.

pre

Pre snapshots should always have a corresponding post snapshot. The intention of pre/post snapshot pairs is to snapshot the filesystem before and after a modification.

post

See pre type.

single

These snapshots have no special relationship to other snapshots.

Note that filesystem-wise all three types are the same.

Snapshot Description and Userdata¶

With each snapshot a description and some userdata can be associated. The description is a string. The userdata is a list of key-value pairs where the keys and values are strings.

Do not use non-ASCII characters for the snapshot description, userdata or any other strings, unless you always use the UTF-8 character encoding.

Automatic Snapshot Creation¶

Next to manual snapshot creation, snapshots are also created automatically.

•A cronjob or systemd timer creates hourly snapshots, if TIMELINE_CREATE is enabled for a config.

•Certain programs like YaST and zypper create pre/post snapshot pairs when modifying the system.

Cleanup Algorithms¶

Snapper provides several algorithms to clean up old snapshots. The algorithms are executed in an hourly cronjob or systemd timer. This can be configured in the corresponding configurations files along with parameters for every algorithm.

number

Deletes old snapshots when a certain number of snapshots is reached.

timeline

Deletes old snapshots but keeps a number of hourly, daily, weekly, monthly, quarterly and yearly snapshots.

empty-pre-post

Deletes pre/post snapshot pairs with empty diffs.

The number and timeline cleanup algorithms can also try to keep the space used by snapshots below a limit and the free space of the filesystem above a limit. For the first condition quota must be setup, see command setup-quota. Additional the NUMBER_LIMIT and TIMELINE_LIMIT variables in the config file must have ranges (min- and max-value). The algorithms will then make two passes:

1.Delete snapshots above the max-value independent of the snapshot and filesystem space.

2.Delete snapshots above the min-value until the limits for the snapshot and filesystem are reached.

The limit for the used space can be configured via the SPACE_LIMIT variable. Note: Only snapshots that have a cleanup algorithm set are taken into account when calculating the space used by snapshots.

The limit for the free space can be configured via the FREE_LIMIT variable.

Note: Since the cleanup is performed asynchronous from creating snapshots the observed snapshots can differ from the expected snapshots according to the limits. Also btrfs stale qgroups can exist temporarily.

Filters¶

Some files keep state information of the system, e.g. /etc/mtab. Such files should never be reverted. To help users, snapper allows one to ignore these files.

Filters are read from the files /etc/snapper/filters/*.txt and /usr/share/snapper/filters/*.txt, where for files with the same name the former location has precedence. Each line in those files specifies a pattern. When snapper computes the difference between two snapshots it ignores all files and directories matching any of those patterns by using fnmatch(3) with the flag FNM_LEADING_DIR.

Note that filters do not exclude files or directories from being snapshotted. For that, use subvolumes or mount points.

GLOBAL OPTIONS¶

-q, --quiet

Suppress normal output. Error messages will still be printed, though.

-v, --verbose

Increase verbosity.

--debug

Turn on debugging.

--utc

Display dates and times in UTC. By default, local time is used.

--iso

Display dates and times in ISO format. ISO format is always used for machine-readable outputs.

-t, --table-style style

Specifies table style. Table style is identified by an integer number.

--abbreviate

Try to abbreviate texts in some columns so that tables fit the width of the screen.

--machine-readable format

Specifies a machine-readable output format. Possible options are csv and json.

--csvout

Sets CSV output format. See RFC 4180[1] for the details, except lines end with a LF, not CR+LF.

--jsonout

Sets JSON output format.

--separator character

Specifies the character separator for CSV output format.

--no-headers

Suppress headers for CSV output format.

-c, --config name

Use specified configuration instead of the default configuration. The default configuration is named "root".

--no-dbus

Operate without a DBus connection.

Use with caution since a running snapperd will not know about modifications made to the system.

-r, --root path

Operate on target root. Only works together with no-dbus and only for some commands.

-a, --ambit ambit

Operate in the specified ambit. Can be used to override the ambit detection. Allowed ambits are auto, classic and transactional.

--version

Print version and exit.

COMMANDS¶

Snapper provides a number of commands. Each command accepts the options listed in the GLOBAL OPTIONS section. These options must be specified before the command name. In addition, many commands have specific options, which are listed in this section. These command-specific options must be specified after the name of the command and before any of the command arguments.

help

Show short help text.

list-configs [options]

List available configurations.

--columns columns

Select columns to show separated by comma.

Possible columns are: config, subvolume.

create-config [options] subvolume

Create a new configuration for a filesystem or subvolume. For this command you will likely need the global option --config, see GLOBAL OPTIONS and CONCEPTS.

-f, --fstype fstype

Manually set filesystem type. Supported values are btrfs, ext4 (discontinued) and lvm. For lvm, snapper uses LVM thin-provisioned snapshots. The filesystem type on top of LVM must be provided in parentheses, e.g. lvm(xfs).

Without this option snapper tries to detect the filesystem.

-t, --template name

Name of template for the new configuration file.

delete-config

Delete a configuration for a filesystem or subvolume. For this command you will likely need to global option --config, see GLOBAL OPTIONS and CONCEPTS.

get-config [options]

Displays the settings of the configuration.

--columns columns

Select columns to show separated by comma.

Possible columns are: key, value.

Columns are not selected when JSON format is used.

set-config configdata

Changes the settings of the configuration. The settings configdata are a list of key-value-pairs separated by spaces and the key and value must be separated by an equal sign, e.g. "NUMBER_CLEANUP=yes NUMBER_LIMIT=10". The value of SUBVOLUME and FSTYPE cannot be changed.

list (ls) [options]

List snapshots.

-t, --type type

Selects type of snapshots to list. Possible values are all, single and pre-post.

--disable-used-space

Disable display of used space.

Calculating the used space needs some time. Thus this option can speedup the listing.

-a, --all-configs

List snapshots from all configs accessible by the user.

--columns columns

Select columns to show separated by comma.

Possible columns are: config, subvolume, number, default, active, date, user, used-space, cleanup, description, userdata, pre-number, post-number, post-date, read-only.

For each snapshot the output consists of several columns. Some need explanation:

#, Pre # and Post #

The number of the snapshot.

For btrfs the number can be followed by a sign. A "-" indicates that the snapshot is the currently mounted snapshot and a "+" indicates that the snapshot will be mounted next time (It is the btrfs default subvolume). If both conditions apply a "*" is displayed.

Used Space

For btrfs the exclusive space of the btrfs quota group corresponding to the snapshot.

Display of used space is automatically disabled if not available, e.g. quota not enabled on btrfs.

create [options]

Create a new snapshot.

-t, --type type

Specifies the type of the new snapshot. Possible values are single, pre and post.

--pre-number number

For post snapshots the number of the pre snapshot must be provided.

-p, --print-number

Print number of the created snapshot.

-d, --description description

Description for the snapshot.

-c, --cleanup-algorithm cleanup-algorithm

Set the cleanup algorithm for the snapshot.

-u, --userdata userdata

Set userdata for the snapshot. The key-value pairs must be separated by comma and the key and value must be separated by an equal sign, e.g. requestid=42,user=arthur.

--command command

Create a pre and post snapshot and run command in between.

--read-only

Create a read-only snapshot. This is the default.

--read-write

Create a read-write snapshot.

--from number

Create a snapshot from the snapshot with the provided number instead of snapshot 0.

--empty

Create an empty snapshot. Only supported on btrfs and with --no-dbus.

modify [options] number

Modify a snapshot.

-d, --description description

New description for snapshot.

-c, --cleanup-algorithm cleanup-algorithm

Set the cleanup algorithm for the snapshot.

-u, --userdata userdata

Set userdata for the snapshot. The key-value pairs must be separated by comma and the key and value must be separated by an equal sign, e.g. requestid=42,user=arthur.

--read-only

Set the snapshot read-only.

--read-write

Set the snapshot read-write.

--default

Set the snapshot as default snapshot. Only for btrfs.

delete (remove|rm) number | number1-number2

Delete a snapshot or a range of snapshots.

-s, --sync

Sync the filesystem after deleting the snapshots. The details depend on the filesystem type.

Btrfs normally asynchronously frees space after deleting snapshots. With this option snapper will wait until the space once used by the deleted snapshots is actually available again.

Snapshot 0 cannot be deleted. For btrfs the currently mounted snapshot and the snapshot that will be mounted next time (the btrfs default subvolume) can also not be deleted.

mount number

Mount a snapshot. Not required for all filesystem types.

umount number

Unmount a snapshot. Not required for all filesystem types.

status [options] number1..number2

Compare the snapshots number1 and number2. This will show a list of files and directories that have been created, modified or deleted in the time between the two snapshots have been made.

-o, --output file

Write output to file file.

The output consists of a string encoding the status followed by the filename. The characters of the status string are:

1.A "+" means the file was created, a "-" means the file was deleted. A "c" means the content of the file has changed and a "t" means the type of the file has changed (e.g. from regular file to directory).

2.A "p" means the permissions are have changed.

3.An "u" means the user ownership has changed.

4.A "g" means the group ownership has changed.

5.A "x" means the extended attribute information has changed.

6.An "a" means the ACL information has changed.

If there is no change a "." is outputted.

diff [options] number1..number2 [files]

Compare the snapshots number1 and number2. This will show a diff of the content of files and directories that have been created, modified or deleted in the time between the two snapshots have been made.

-i, --input file

Read files to diff from file file.

--diff-cmd command

Command used for comparing files. The default is /usr/bin/diff --new-file --unified. The two files to compare are passed as parameters to the command.

-x, --extensions options

Extra options passed to the diff command.

undochange [options] number1..number2 [files]

Undo changes done between snapshot number1 and number2.

-i, --input file

Read files for which to undo changes from file file.

rollback [options] [number]

Creates two new snapshots and sets the default subvolume. Per default the system boots from the default subvolume of the root filesystem. The exact actions depend on whether a number is provided or not:

•Without a number, a first read-only snapshot of the default subvolume is created. A second read-write snapshot of the current system is created. The system is set to boot from the second snapshot.

•With a number, a first read-only snapshot of the current system is created. A second read-write snapshot is created of number. The system is set to boot from the second snapshot.

Rollback is only supported with btrfs and requires a properly configured system.

-p, --print-number

Print number of the second created snapshot.

-d, --description description

Description for the snapshot.

-c, --cleanup-algorithm cleanup-algorithm

Set the cleanup algorithm for the snapshot.

-u, --userdata userdata

Set userdata for the snapshot. The key-value pairs must be separated by comma and the key and value must be separated by an equal sign, e.g. requestid=42,user=arthur.

The rollback command also sets the description, the cleanup algorithm and some userdata unless the values are specified on the command line. This will automate cleanup of snapshots created by rollbacks.

In other ambits than classic the rollback command does what is required to do a rollback. Anyway it is recommended to use specific programs in that case.

setup-quota

Sets up quota. Currently only supported with btrfs.

cleanup [options] cleanup-algorithm

Run the cleanup algorithm cleanup-algorithm. Currently implemented cleanup algorithms are number, timeline and empty-pre-post. To run all cleanup algorithms, all can be provided as cleanup-algorithm.

--path path

Cleanup all configs affecting path. Only useful for btrfs.

--free-space free-space

Try to make free-space available. Only useful for btrfs.

xadiff number1..number2 [files]

Compare the extended attributes between snapshot number1 and number2. See examples below:

•+:user.foo for created attributes

•-:user.bar for removed attributes

•-+:security.selinux for modified attributes

PERMISSIONS¶

Non-root users can be allowed to use a configuration by setting ALLOW_USERS or ALLOW_GROUPS in the config file. For all operations to work, the user must also be able to read and access the .snapshots directory inside the subvolume. The .snapshots directory must be owned by root and must not be writable by anybody else.

Here are some methods how to achieve that:

•Make the directory accessible for everyone:

chmod a+rx .snapshots

•Make the directory accessible for a group the user belongs to, e.g.:

chown :users .snapshots

•Make the directory accessible for the user using ACLs, e.g.:

setfacl -m u:tux:rx .snapshots

The last method can be performed by snapper, see the SYNC_ACL setting in snapper-configs(5).

PLUGINS¶

snapper can execute external scripts after certain actions. Scripts have to be placed in /usr/lib/snapper/plugins. The name has to start with a digit, execution order is alphabetical.

The first argument of a script is the action snapper executed. The following actions are defined:

create-config-pre subvolume fstype

Executed before a new config is created

create-config-post subvolume fstype

Executed after a new config was created

delete-config-pre subvolume fstype

Executed before a config is deleted

delete-config-post subvolume fstype

Executed after a config was deleted

create-snapshot-pre subvolume fstype snapshot-number

Executed before a new snapshot is created

create-snapshot-post subvolume fstype snapshot-number

Executed after a new snapshot was created

modify-snapshot-pre subvolume fstype snapshot-number

Executed before a snapshot is modified

modify-snapshot-post subvolume fstype snapshot-number

Executed after a snapshot was modified

delete-snapshot-pre subvolume fstype snapshot-number

Executed before a snapshot is removed

delete-snapshot-post subvolume fstype snapshot-number

Executed after a snapshot was removed

set-default-snapshot-pre subvolume fstype snapshot-number

Executed before the default snapshot is changed

set-default-snapshot-post subvolume fstype snapshot-number

Executed after the default snapshot was changed

rollback-post subvolume fstype old-snapshot-number new-snapshot-number

Executed after a rollback was done

More actions and arguments can be added any time. Using snapper in the plugins is not allowed.

It is undefined whether the plugins are called from the client (snapper) or server (snapperd).

FILES¶

/etc/sysconfig/snapper

Global configuration file.

/etc/snapper/configs

Directory containing configuration files.

/etc/snapper/config-templates

Directory containing configuration templates.

/usr/share/snapper/config-templates

Fallback directory containing configuration templates.

/etc/snapper/filters/*.txt

Filter files.

/usr/share/snapper/filters/*.txt

Fallback filter files.

/var/log/snapper.log

Logfile. Please include this file in bug reports.

EXIT STATUS¶

Normally the exit status is 0. If an error occurred the exit status is 1. It is also an error if the exit status of a plugin is not 0.

NOTES¶

There is no mechanism to ensure consistency of the files while a snapshot it made. E.g. the files of a database can be inconsistent while the database is running.

Consistency after undochange is not guaranteed. E.g. when the creation of a user is undone, there might still exist files from that user.

Support for individual filesystems, rollback and extended attributes are compile-time options and may not be available.

HOMEPAGE¶

http://snapper.io/

AUTHORS¶

Arvin Schnell <aschnell@suse.com>

NOTES¶

1.: RFC 4180

https://tools.ietf.org/html/rfc4180

2024-10-24

0.12.0

Source file:	snapper.8.en.gz (from snapper 0.12.0-1.1)
Source last updated:	2024-11-05T09:50:51Z
Converted to HTML:	2024-12-03T01:53:10Z

NAME¶

SYNOPSIS¶

DESCRIPTION¶

CONCEPTS¶

Configurations¶

Snapshots¶

Snapshot Description and Userdata¶

Automatic Snapshot Creation¶

Cleanup Algorithms¶

Filters¶

GLOBAL OPTIONS¶

COMMANDS¶

PERMISSIONS¶

PLUGINS¶

FILES¶

EXIT STATUS¶

NOTES¶

HOMEPAGE¶

AUTHORS¶

SEE ALSO¶

NOTES¶