Ubuntu Manpage: snapper - Command-line program for filesystem snapshot management

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 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.

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

• A cron-job creates hourly snapshots.

• 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 cron-job. 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 algorithm can also try to keep the space used by snapshots
below a limit. For that quota must be setup, see command setup-quota, and the 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 used space.

2. Delete snapshots above the min-value until the limit for the used space is 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
used space.

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.

Each line in all files /etc/snapper/filters/*.txt 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.

       --iso
           Display dates and times in ISO format.

       -t, --table-style
           Specifies table style. Table style is identified by an integer number.

       -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.

       --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
List available configurations.

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 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
Displays the settings of the configuration.

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.

-a, --all-configs
List snapshots from all configs accessible by the user.

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.

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.

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.

setup-quota
Sets up quota. Currently only supported with btrfs.

cleanup cleanup-algorithm
Run the cleanup algorithm cleanup-algorithm. Currently implemented cleanup algorithms
are number, timeline and empty-pre-post.

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.

       /etc/snapper/filters/*.txt
           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>

NAME

SYNOPSIS

DESCRIPTION

CONCEPTS

GLOBAL OPTIONS

COMMANDS

PERMISSIONS

FILES

NOTES

HOMEPAGE

AUTHORS

SEE ALSO