What is snap linux

Snap is a software deployment and package management system. The packages are called ‘snaps’ and the tool for using them is ‘snapd’, which works across a range of Linux distributions and allows, therefore, distro-agnostic upstream software deployment. Snap was originally designed and built by Canonical.

snapd is a REST API daemon for managing snap packages. Users can interact with it by using the snap client, which is part of the same package.

Snaps can be confined using AppArmor which is now enabled in the default kernel. Consult relevant wiki pages to find steps for enabling AppArmor in your system.

Installation

snapd supports the AppArmor security model if it is enabled on your system, to install it follow AppArmor#Installation.

If you are using AppArmor, enable and start both apparmor.service and snapd.apparmor.service .

Configuration

To launch the snapd daemon when snap tries to use it, start and/or enable the snapd.socket .

Usage

The snap tool is used to manage the snaps.

Finding

To find snaps to install, you can query the Ubuntu Store with:

Installing

Once you found the snap you are looking for you can install it with:

This requires root privileges. Per user installation of snaps is not possible, yet. This will download the snap into /var/lib/snapd/snaps and mount it to /var/lib/snapd/snap/snapname to make it available to the system.

It will also create mount units for each snap and add them to /etc/systemd/system/multi-user.target.wants/ as symlinks to make all snaps available when the system is booted. Once that is done you should find it in the list of installed snaps together with its version number, revision and developer using:

You can also sideload snaps from your local hard drive with:

Updating

To update your snaps manually use:

Snaps are refreshed automatically according to snap refresh.timer setting.

To view the next/last refresh times use:

To set a different refresh time, eg. twice a day:

See system options documentation page for details on customizing the refresh time.

Removing

Snaps can be removed by executing:

Tips and tricks

Classic snaps

Some snaps (e.g. Skype and Pycharm) use classic confinement. However, classic confinement requires the /snap directory, which is not FHS-compliant. The snapd package does not ship this directory, however the user can manually create a symbolic link between /var/lib/snapd/snap and /snap to allow the installation of classic snaps:

Confinement

When using AppArmor, snapd will generate the same profiles for snaps as on Ubuntu. The AppArmor parser is smart enough to drop the rules that are not yet supported by the mainline kernel.

To verify that basic confinement is working, install hello-world snap. Then run the following:

The denial was caused by AppArmor and should have been logged:

If you do not see the denial, verify that the profiles were loaded:

Also, you can check what sandbox features are available in the system according to snapd:

Troubleshooting

Text unreadable

If you are seeing squares instead of readable characters, you need to clear the font cache:

Snapctl also stores internal caches for each individual snap, which need to be cleared seperately. First, find them by running:

Then either remove them individually or use this simple loop.

Finally, Restart your session.

Error: cannot mount squashfs

Snap packages use the SquashFS file system. In the event of an error similar to the following:

you may verify that the SquashFS kernel module is loaded with

Graphical management

Both Gnome Software Center and KDE Discover can provide native snap support. For KDE Discover install discover-snap AUR package.

Support

Arch Linux related mailing lists and other official Arch Linux support channels are not an appropriate place to request help with snaps on Arch Linux. An appropriate place to ask for support is the Snapcraft forum.

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Snap (Русский)

snapd это REST API демон для управления snap-пакетами («snaps»). Пользователи могут взаимодействовать с ним с помощью snap клиента, входящего в тот же пакет.

Установка

В пакет входит snapd демон, а также snap-confine, который обеспечивает монтирование, изоляцию и запуск snap-пакетов.

Настройка

В пакет также входят несколько systemd unit файлов, которые обеспечивают возможность обновления всех установленных snap-пакетов, при выходе новой версии.

Для того чтобы snapd демон запускался, когда snap обращается к нему, запустите snapd.socket .

Вы также можете активировать его при старте системы.

Для того чтобы автоматически обновлять пакеты активируйте snapd.refresh.timer :

Управление snap-пакетами

Для управления пакетами используется утилита snap.

Поиск

Для поиска пакетов, доступных для установки используйте команду find:

Это выведет список всех доступных пакетов. Для поиска конкретного пакета используйте:

Установка пакетов

Установить snap-пакет можно с помощью команды:

Установка требует root привилегий. Установка с правами пользователя на данный момент невозможна. При установке snap загружается в /var/lib/snapd/snaps и монтируется в /snap/имя_пакета .

Кроме того, создаются также юнит-файлы для каждого snap-пакета и добавляются в /etc/systemd/system/multi-user.target.wants/ , для того чтобы snap-пакеты монтировались при каждом запуске системы. Вы можете просмотреть список установленных пакетов командой:

Вы также можете устанавливать snap-пакеты локально, с жесткого диска:

Обновление пакетов

Для того чтобы обновить snap-пакеты выполните:

Удаление пакетов

Для того чтобы удалить пакет выполните:

Удаление

Удаление пакета snapd AUR не приводит к удалению всех каталогов и файлов, которые создаются при его использовании. Лучше всего удалить все snap-пакеты с помощью snap remove, перед тем как удалять сам пакет. Однако, на данный момент невозможно удалить snap-пакет ubuntu-core. Для того чтобы полностью удалить все файлы следуйте инструкции ниже.

1. Отмонтируйте все активные snap-пакеты из /snap .

2. Удалите следующие каталоги:

3. Удалите все файлы, отвечающие за монтирование snap-пакетов из /var/lib/snapd/snaps в /snap при загрузке.

Советы и рекомендации

Classic snaps

Some snaps (e.g. Skype and Pycharm) use classic confinement. However, classic confinement requires the /snap directory, which is not FHS-compliant. Therefore, the snapd package does not ship this directory. However, if the user wants to, he can manually create a symlink from /snap to /var/lib/snapd/snap , to allow the installation of classic snaps:

Помощь

Почтовая рассылка Arch Linux и другие официальные каналы поддержки Arch Linux не являются подходящим местом для запроса помощи по snap-пакетам на Arch Linux. Подходящим местом для запроса поддержки является Snapcraft forum.

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Getting started

A snap is a bundle of an app and its dependencies that works without modification across many different Linux distributions. Snaps are discoverable and installable from the Snap Store, an app store with an audience of millions.

The following sections provide a basic overview of using snaps, from installation to management and manipulation.

Install snapd

The snapd daemon manages the snap environment on the local system. Its installation will include the snap tool for interacting with snaps. You can check both are installed by attempting to run snap version on the command line:

If all is well, version numbers for the main system components will be output, as shown above, albeit with potentially different versions and Linux distribution identifier.

If the snap command is not found, or if the command takes a while to respond before reporting that snapd is unavailable, make sure snapd is properly installed before continuing.

The «$» above represents the command line prompt. Sample commands come after this prompt with any relevant output shown below.

Find a snap

With snapd installed, snaps can be discovered, searched for, and installed from the Snap Store, from the Snap Store desktop app, and directly from the command line. For example, the following command returns a list of media players:

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

Learn about a 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:

Install a snap

Installing a snap is straightforward:

Channels are an important snap concept. They define which release of a snap is installed and tracked for updates. The stable channel is used by default, but opting to install from a different channel is easily accomplished:

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

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

Run apps and commands from snaps

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:

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

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

List installed snaps

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

Some snaps, such as core listed above, are installed by 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:

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:

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:

This operation will revert both the snap revision and the 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.

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:

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 every installed snap, and also highlights which particular revisions are disabled at the moment:

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.

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:

Remove a snap

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

By default, all of a snap’s revisions are also removed. To remove a specific revision, add the —revision= 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:

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

Next steps

Last updated 2 days ago.

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A Beginners Guide to Snaps in Linux – Part 1

In the past few years, the Linux community has been blessed with some remarkable advancements in the area of package management on Linux systems, especially when it comes to universal or cross-distribution software packaging and distribution. One of such advancements is the Snap package format developed by Canonical, the makers of the popular Ubuntu Linux.

What are Snap Packages?

Snaps are cross-distribution, dependency-free, and easy to install applications packaged with all their dependencies to run on all major Linux distributions. From a single build, a snap (application) will run on all supported Linux distributions on desktop, in the cloud, and IoT. Supported distributions include Ubuntu, Debian, Fedora, Arch Linux, Manjaro, and CentOS/RHEL.

Snaps are secure – they are confined and sandboxed so that they do not compromise the entire system. They run under different confinement levels (which is the degree of isolation from the base system and each other). More notably, every snap has an interface carefully selected by the snap’s creator, based on the snap’s requirements, to provide access to specific system resources outside of their confinement such as network access, desktop access, and more.

Another important concept in the snap ecosystem is Channels. A channel determines which release of a snap is installed and tracked for updates and it consists of and is subdivided by, tracks, risk-levels, and branches.

The main components of the snap package management system are:

snapd – the background service that manages and maintains your snaps on a Linux system.
snap – both the application package format and the command-line interface tool used to install and remove snaps and do many other things in the snap ecosystem.
snapcraft – the framework and powerful command-line tool for building snaps.
snap store – a place where developers can share their snaps and Linux users search and install them.

Besides, snaps also update automatically. You can configure when and how updates occur. By default, the snapd daemon checks for updates up to four times a day: each update check is called a refresh. You can also manually initiate a refresh.

How to Install Snapd in Linux

As described above, the snapd daemon is the background service that manages and maintains your snap environment on a Linux system, by implementing the confinement policies and controlling the interfaces that allow snaps to access specific system resources. It also provides the snap command and serves many other purposes.

To install the snapd package on your system, run the appropriate command for your Linux distribution.

After installing snapd on your system, enable the systemd unit that manages the main snap communication socket, using the systemctl commands as follows.

On Ubuntu and its derivatives, this should be triggered automatically by the package installer.

Note that you can’t run the snap command if the snapd.socket is not running. Run the following commands to check if it is active and is enabled to automatically start at system boot.

Check Snapd Service Status

Next, enable classic snap support by creating a symbolic link between /var/lib/snapd/snap and /snap as follows.

To check the version of snapd and snap command-line tool installed on your system, run the following command.

Check Snapd and Snap Version

How to Install Snaps in Linux

The snap command allows you to install, configure, refresh and remove snaps, and interact with the larger snap ecosystem.

Before installing a snap, you can check if it exists in the snap store. For example, if the application belongs in the category of “chat servers” or “media players“, you can run these commands to search for it, which will query the store for available packages in the stable channel.

Find Applications in Snap Store

To show detailed information about a snap, for example, rocketchat-server, you can specify its name or path. Note that names are looked for both in the snap store and in the installed snaps.

Get Info About Application in Snap

To install a snap on your system, for example, rocketchat-server, run the following command. If no options are provided, a snap is installed tracking the “stable” channel, with strict security confinement.

Install Application from Snap Store

You can opt to install from a different channel: edge, beta, or candidate, for one reason or the other, using the —edge , —beta , or —candidate options respectively. Or use the —channel option and specify the channel you wish to install from.

Manage Snaps in Linux

In this section, we will learn how to manage snaps in Linux system.

Viewing Installed Snaps

To display a summary of snaps installed on your system, use the following command.

List Installed Snaps

To list the current revision of a snap being used, specify its name. You can also list all its available revisions by adding the —all option.

List All Installation Versions of Snap

Updating and Reverting Snaps

You can update a specified snap, or all snaps in the system if none are specified as follows. The refresh command checks the channel being tracked by the snap and it downloads and installs a newer version of the snap if it is available.

Refresh a Snap

After updating an app to a new version, you can revert to a previously used version using the revert command. Note that the data associated with the software will also be reverted.

Revert a Snap to Older Version

Now when you check all revisions of mailspring, the latest revision is disabled, a previously used revision is now active.

Check Revision of Snap

Disabling/Enabling and Removing Snaps

You can disable a snap if you do not want to use it. When disabled, a snap’s binaries and services will no longer be available, however, all the data will still be there.

If you need to use the snap again, you can enable it back.

To completely remove a snap from your system, use the remove command. By default, all of a snap’s revisions are removed.

To remove a specific revision, use the —revision option as follows.

It is key to note that when you remove a snap, its data (such as internal user, system, and configuration data) is saved by snapd (version 2.39 and higher) as a snapshot, and stored on the system for 31 days. In case you reinstall the snap within the 31 days, you can restore the data.

Conclusion

Snaps are becoming more popular within the Linux community as they provide an easy way to install software on any Linux distribution. In this guide, we have shown how to install and work with snaps in Linux. We covered how to install snapd, install snaps, view installed snaps, update and revert snaps, and disable/enable and remove snaps.

You can ask questions or reach us via the feedback form below. In the next part of this guide, we will cover managing snaps (commands, aliases, services, and snapshots) in Linux.

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What is snap linux