Provided by: snapper_0.10.2-1_amd64 
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 a daily 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 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.
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.
--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.
-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.
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.
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.
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).
FILES
/etc/default/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.
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>
SEE ALSO
snapper-configs(5), snapper-zypp-plugin(8), pam_snapper(8), btrfs(8), lvm(8), attr(5),
acl(5)
NOTES
1. RFC 4180
https://tools.ietf.org/html/rfc4180