Quickstart guide

A snap is a bundle of one or more applications (“apps”) and their dependencies that works without modification across many different Linux distributions. Snaps are discoverable and installable from the Snap Store, a public app store with an audience of millions.

This is a long tutorial, but it doesn’t need to be completed in a single session. We’d suggest going through the first few steps and then playing with what you’ve learnt, then come back when you feel comfortable and wish to further your knowledge.

By the end of this tutorial, you’ll have a good understanding of how to use snaps, from installing your favourite desktop applications, or tightly confined services, to controlling their access to your system, making backups, and reverting a snap from one revision to a previous revision.

Requirements

This tutorial is suitable for users on any system that supports snaps, with a preference for Ubuntu.

Snaps have been designed to be as accessible as possible, and while they can be easily installed and removed via a graphical package manager, such as Ubuntu Software Centre, you do need to use the terminal to get the most out of them.

As a result, this will be easier if you’re already familiar with basic terminal commands, but even if you’re not, this tutorial itself might be the perfect introduction to get you started.

Find a snap

There are snaps for many popular applications, including Spotify, Slack and the Chromium web browser.

The best way to find new snaps is to use the online Snap Store, and either search for apps and words you’re interested in, such as “music” or “maths”, or use the category lists.

The Snap Store frontend is also installed by default on Ubuntu, and can itself be installed as a snap on other systems. It offers the same user experience as the online store.

The snap terminal command, however, is the primary interface to all of snap’s packaging features. It’s easily run by first opening a terminal and typing snap followed by a command. Typing snap on its own will show some brief help text and list of example commands to try, including the find command.

To search for snaps with ‘media player’ in either their names or descriptions, type snap find "media player" into your terminal:

$ snap find "media player"
Name  Version  Developer    Notes  Summary
(...)
vlc   3.0.4     videolan✓   -      The ultimate media player.
mpv   0.26.0    casept      -      a free, open source, and cross-platform media player.  
(...)

The alongside videolan in the above output indicates that the snap publisher has been verified.

The find output can be limited to snaps from specific categories, such as music-and-audio, with the additional --section= argument:

$ snap find "media player" --section="featured"
Name        Version  Publisher  Notes  Summary
foobar2000  1.6.12   mmtrt      -      foobar2000 is an advanced freeware audio player.
vlc         3.0.16   videolan✓  -      The ultimate media player

Snap categories

Typing snap find without any arguments will return a list of suggested snaps and those suggestions can also be filtered to a category with the same --section= argument. The following section names are valid:

art-and-design books-and-reference development devices-and-iot
education entertainment featured finance
games health-and-fitness music-and-audio news-and-weather
personalisation photo-and-video productivity science
security server-and-cloud social utilities

Learn about your snap

The snap info command makes it easy to find more details about a specific snap. These details include what a snap does, who publishes it, the command(s) it provides and which channel versions are available for installation:

$ snap info vlc
name:      vlc
summary:   The ultimate media player
publisher: VideoLAN✓
contact:   https://www.videolan.org/support/
description: |
  VLC is the VideoLAN project's media player.
---
snap-id: RT9mcUhVsRYrDLG8qnvGiy26NKvv6Qkd
commands:
  - vlc
channels:
  latest/stable:    3.0.16                      2021-06-28 (2344) 310MB -
  latest/candidate: 3.0.16                      2021-06-28 (2344) 310MB -
  latest/beta:      3.0.18-rc-38-gcc4c37ebb3    2022-09-20 (3021) 335MB -
  latest/edge:      4.0.0-dev-20763-g15bf12a0f3 2022-09-20 (3022) 659MB -

Add the --verbose option to info to retrieve more details on the snap, including expanded notes and details on which base the snap uses.

The final part of the above output lists the channels for the snap. Channels are an important snap concept because they define which release of a snap is installed and tracked for updates. The latest/stable channel is used by default, but opting to install from a different channel is easily accomplished.

Install the snap

Installing a snap is straightforward. Type snap install followed by the name of the snap you wish to install:

sudo snap install vlc

As mentioned in the previous step, a channel can be specified to install a version of the snap that follows a different build and release cycle, such as the latest/beta to trade some stability for the latest cutting edge features.

channels can be used to install a version of the snap that follows a more cutting edge feature release, such as a beta or edge channel,

sudo snap install --channel=edge vlc

After installation, the channel being tracked can be changed with:

sudo snap switch --channel=stable vlc

Which snaps are released to which channels is entirely up to the snap publisher.

Using sudo:

The sudo command ensures the command following it is executed as the root administrative user.

While not a requirement for using snaps, creating an Ubuntu One/SSO account, and authenticating once with snap login <email-address>, removes the need to use sudo with snap commands.

Run apps and commands from the snap

A snap’s installed applications can be found under /snap/bin, and subsequently, often added to $PATH. This makes commands directly accessible from the command line.

For example, the command installed via the VLC snap is simply vlc:

$ which vlc
/snap/bin/vlc

If executing a command directly doesn’t work, try prefixing it with the /snap/bin path:

/snap/bin/vlc

Connect an interface

Interfaces are one of snaps best features because they allow (or deny) access to a resource outside of a snap’s confinement.

An interface is most commonly used to enable a snap to access a webcam, sound playback or recording, your network, and your $HOME directory. But which interfaces a snap requires, and provides, is very much dependent on the type of snap and its own requirements.

To see which interfaces a snap is using, and which interfaces it could use but isn’t, type snap connections <snapname>:

$ snap connections vlc
Interface       Plug                   Slot                 Notes
audio-playback  vlc:audio-playback     :audio-playback      -
audio-record    vlc:audio-record       -                    -
camera          vlc:camera             -                    -
desktop         vlc:desktop            :desktop             -
home            vlc:home               :home                -
(...)

In the above output, the camera interface is not connected because its slot is empty. This means VLC cannot access any connected cameras.

To allow a camera to be accessible to VLC, the interface can be connected with the snap connect command:

snap connect vlc:camera

The Ubuntu Software/Snap Store desktop application can also be used to enable and disable interface connections.

To access the interface management functions, either search for an installed snap, or select it from the Installed view. The interfaces for the selected application can then be viewed by selecting Permissions :

Snap Store VLC interface connections

As you can see the output from snap connections vlc, and in the above image, VLC already has access a user’s /home directory because the home interface is connected to the system $HOME directory. This is an automatic connection, and is granted to certain interfaces and snaps when an interface provides fundamental functionality, such as VLC accessing your personal video and audio files.

Where snaps store data

Most snaps use strict confinement to isolate both their execution environments and their data from your system (see Snap Confinement for further details). A confined snap that needs user-access to files will most likely use the home interface to bridge this confinement gap, allowing you to save and load files from your home directory automatically.

You can see whether the home interface is being used in the output to snap connections <snap name>:

$ snap connections nethack
Interface  Plug          Slot   Notes
home       nethack:home  :home  -

Regardless of whether the home interface is used or not, a snap can also store user data, such as a database or configuration files, within its own directory under $HOME/snap. Data within this snap-specific directory is stored in one of two further directories, depending on whether the data needs to be tied to a specific release, or whether it can be used across multiple releases.

Data for a specific release is stored within a directory named after the revision of a release. This is a numeric value, such as 55 or 56. The data for each specific revision is often copied from one release to the next, so that reverting from one revision to a previous revision will restore a working configuration, for instance. The snap directory also contains a symbolic link called current that points to the snap revision currently active.

Data that can be shared across releases is stored in a directory called common, and might include image or audio caches, or a database. This data is not copied between releases.

For more details on where snaps store their data, see Data locations.

List installed snaps

Use snap list to show a list of snaps installed on your system:

$ snap list
Name     Version        Rev   Tracking  Publisher   Notes
core     16-2.35.1      5419  beta      canonical✓  core
spotify  1.0.88.353     19    stable    spotify✓    -
vlc      3.0.4          555   stable    videolan✓   -

Some snaps, such as core listed above, are installed automatically by snapd to satisfy the requirements of other snaps.

Update an installed snap

Snaps are updated automatically. However, to manually check for updates, use the following command:

sudo snap refresh vlc

The above will check the channel being tracked by the snap. If a newer version of the snap is available, it will be downloaded and installed.

Changing the channel being tracked and refreshing the snap can be accomplished with a single command:

sudo snap refresh --channel=beta vlc

Updates are automatically installed within 6 hours of a revision being made to a tracked channel, keeping most systems up-to-date. This schedule can be tuned via configuration options.

Versions and revisions

Versions and revisions convey different details about one specific release of a snap:

  • Version : the version of the software being packaged, as assigned by the developers
  • Revision: the sequence number assigned by the store when the snap file was uploaded

The version is a string that was assigned to a project by its developers, according to their development practices. It tells the user what content to expect from a snap. The revision is an automatic number assigned by the Snap store, giving the snap a unique identity within the channel.

Neither the version nor the revision enforce an order of release. The local system will simply attempt to install whatever snap is recommended by the publisher in the channel being tracked.

Revert to a previously used snap

A snap may be reverted to a previously used revision with the snap revert command:

$ sudo snap revert vlc
vlc reverted to 3.0.5-1

This operation will revert both the snap revision and the configuration data associated with the software. If the previously used revision of the snap is from a different channel, that snap will be installed but the channel being tracked won’t change.

User data, such as data generated by the snap and stored in a database, is often stored in a common directory and will not be reverted. See Data locations for more details on what information is stored and where.

A snap won’t automatically update to a version previously reverted from, and the output from snap refresh will continue to state All snaps up to date. A reverted snap will be automatically updated when a new and different revision is made available by the publisher.

However, explicitly adding the snap name to snap refresh will update the snap, regardless of whether the latest revision was previously reverted from or not:

$ snap list --all vlc
Name  Version  Rev  Tracking  Publisher  Notes
vlc   3.0.5-1  768  stable    videolan✓  -
vlc   3.0.6    770  stable    videolan✓  disabled
$ sudo snap refresh
All snaps up to date.
$ sudo snap refresh vlc
vlc 3.0.6 from VideoLAN✓ refreshed

On an Ubuntu Core system, such as Ubuntu Core 18 and Ubuntu Core 16, reverting twice will work too. This is because snapd attempts to keep three revisions of a snap: the most recently installed plus the two previous installations. On classic systems like Ubuntu 18.04 LTS or Ubuntu 16.04 LTS, two revisions are retained by default. This behaviour can be modified with the refresh.retain system option.

List all available revisions

The following command lists all revisions available for all installed snaps, and also highlights which particular revisions are disabled at the moment:

$ snap list --all
Name          Version  Rev    Tracking          Publisher         Notes
alacritty     0.8.0    46     latest/stable     snapcrafters✪   classic
ascii-patrol  1.7      152    latest/stable     mr-gumix          disabled
ascii-patrol  1.7      159    latest/stable     mr-gumix          -
asciinema     2.1.0    32     latest/stable     asciinema         classic
asciinema     2.0.2    16     latest/stable     asciinema         disabled,classic
[...]

Please note that ✪ in the output above, shows Star Developers, who are active maintainers in the community.

Adding a snap name to the snap list --all command will return results only for that snap:

$ snap list --all vlc
Name   Version         Rev   Tracking  Publisher   Notes
vlc    4.0.0-dev-4620  560   edge      videolan✓   disabled   
vlc    3.0.4           555   edge      videolan✓   -

A previously used snap that was reverted from will display disabled in the Notes column of the output.

Manually keeping track of which snap revisions available is generally unnecessary. A single revision will only ever be in use at a time, and snapd will remove old revisions automatically.

Create and restore a snapshot

A snapshot is a copy of the user, system and configuration data stored by snapd for one or more snaps on your system, and a snapshot of the data found in both $HOME/snap/<snap-name> and /var/snap/<snap-name> is stored in /var/lib/snapd/snapshots/ (see Data locations for more details).

Snapshots are generated manually with the snap save command and automatically when a snap is removed. A snapshot can be used to backup the state of your snaps, revert snaps to a previous state and to restore a fresh snapd installation to a previously saved state.

The snap save command creates a snapshot for all installed snaps, or if declared individually, specific snaps:

$ sudo snap save
Set  Snap         Age    Version               Rev   Size   Notes
30   core         1.00s  16-2.37~pre1          6229   250B  -
30   core18       886ms  18                    543    123B  -
30   go           483ms  1.10.7                3092   387B  -
30   vlc          529ms  3.0.6                 770   882kB  -

The restore command replaces the current user, system and configuration data with the corresponding data from the specified snapshot:

$ sudo snap restore 30
Restored snapshot #30.

By default, this command restores all the data for all the snaps in a snapshot. You can restore data for specific snaps by simply listing them after the command, and for specific users with the --users=<usernames> argument.

Excluding a snap’s system and configuration data from snap restore is not currently possible.

See Snapshots for further details on creating, exporting, importing and validating snapshots.

Disable and enable snaps

If a snaps is temporarily undesired, it can be disabled and later enabled again. This avoids having to remove and reinstall them in the system:

$ sudo snap disable vlc
vlc disabled

$ sudo snap enable vlc
vlc enabled

Remove a snap

To remove a snap from your system, along with its internal user, system and configuration data, use the remove command:

$ sudo snap remove vlc
vlc removed

Add the --no-wait option to return immediately to the command prompt and run the removal in the background.

By default, all of a snap’s revisions are also removed. To remove a specific revision, add the --revision=<revision-number> argument to the remove command.

Prior to removal (except on Ubuntu Core systems), a snap’s internal user, system, and configuration data is saved as a snapshot (snapd 2.39+), and retained for 31 days.

To remove a snap without generating a snapshot, use the additional --purge argument:

$ sudo snap remove vlc --purge
vlc removed

However, a snapshot can be used to restore the state of your snap upon reinstallation. See Snapshots for further details.

1 Like

Nice doc :smiley:

A couple of the examples are missing the snap name - for example:

$ snap switch --channel=stable

…should surely be:

$ snap switch --channel=stable vlc ?

Similarly:

$ snap refresh --channel=candidate

Regards,

1 Like

Thanks! … and fixed!

Great guide.
I am wondering whether “sudo” is needed when trying to install a snap.
If you are running a distro in a virtualized environment, then you need “sudo snap”. Otherwise, you do not.

Is that the case?

I’m not sure I get your question, so please correct me if I’m on the wrong track.

The sudo is needed because in general it seems nice to assume people are not running all commands as root, but instead as their usual user, so the sudo increases the privilege of the command following it to that of the system administrator. That said, when running commands inside a lxd container or similar, the root is more also more isolated and thus more natural, so you might not need it.

I posted a dedicated question at "sudo snap install" or just "snap install"?

(moderation: further content dropped so we move the conversation to your topic)

The ‘$ snap version’ command line output is system dependent i.e. on Ubuntu 18.04 LTS the output is:
snap 2.36.1
snapd 2.36.1
series 16
ubuntu 18.04
kernel 4.15.0-39-generic

Perhaps this could be clarified in the document.

PS: Apologies to all if this entry is mis-placed.

Good point - thanks for letting us know. I’ll update the post (and yes, this is the right place!).

Thanks!

This topic should document the snap run command, just in case one has install multiple distributions of the same command.

A post was split to a new topic: Issues with snap info

This topic should also include the installation and initialization of multipass, since snapcraft defaults to it.

Simply installing the multipass snap is not enough apparently, I had to execute multipass launch to make sure multipass is initialized before running snapcraft. I’m not sure if there is an easier way to initialize multipass.

I think you may mean we need to update Snapcraft overview to show how multipass is initialised? I’ll check with a fresh install and see whether some extra steps are needed. The last time I did this, multipass was installed automatically.

Yes, I’m talking about Snapcraft overview. I’m not sure how my comment ended up on this page. This is what I did:

  1. snap install snapcraft --classic
  2. snap install multipass --classic
  3. snapcraft in the directory of a snap.

Step 3 gave me errors until I executed multipass launch. I’m not sure what happens when you don’t install multipass manually, I have not tried that.

This is in reference to this document: https://snapcraft.io/docs/getting-started

Just pointing out that the image immediately following this text seems to show that the data associated with the snap is retained if it has been modified – which is it?

Thanks for flagging this, and you’re right that the image is misleading. I’ll either update it or replace it, and add further details to the text to make this clearer. The answer actually depends on where the snap stores its data.

If the data is in a common directory (SNAP_USER_COMMON or SNAP_COMMON for the snap developer) then there’s only one instance of the data available across all revisions of the snap, regardless of any revision-specific modifications.

If it’s within a revision-specific folder (SNAP_DATA and SNAP_USER_DATA for the snap developer), then the diagram is correct - data associated with a revision normally migrates forwards, but not backwards after a revert.

Additionally, there’s also data saved in a Snapshot.

This is covered in Data locations, but I agree, it should be simplified and rewritten here.

A couple(?) observations.

  1. Is it worth mentioning the “–verbose” option to “snap info”, as in “snap info --verbose vlc”?

  2. Further down:

"List all available revisions

The following command lists all revisions available for every installed snap, and also highlights which particular revisions are disabled at the moment:

$ snap list --all vlc"

No, that command does not list all revisions “available for every installed snap”, only for vlc.

  1. “Adding /snap/bin to your default $PATH makes running snaps that don’t automatically add themselves more convenient.”

Interestingly, not only should the user not have to do that (on my Ubuntu 22.04 system, that entry is already appended to my PATH) but, oddly, it’s appended twice. As in, it appears that installing snapd somehow adds that directory to one’s PATH twice. Doesn’t hurt, of course, just unnecessary.

  1. Is it worth mentioning the “–no-wait” option for “snap remove”?

Thanks for all these suggestions. I’ve updated the doc to incorporate all of them.

Regarding the discussion of whether or not to keep including “sudo” in sample commands, perhaps early on in this page, add an emphatic note that one can register for a SSO account, then use “snap login” to obviate the need for constant “sudo”.

Good idea. I’ve added some details to the info block explaining the use of sudo. Thanks!

I think the “by” marked bold should be removed.