Snap is a software

packaging Packaging is the science, art and technology of enclosing or protecting products for distribution, storage, sale, and use. Packaging also refers to the process of designing, evaluating, and producing packages. Packaging can be described as a co ...

and

deployment Deployment may refer to: Engineering and software Concepts * Blue-green deployment, a method of installing changes to a web, app, or database server by swapping alternating production and staging servers * Continuous deployment, a software en ...

system developed by

Canonical The adjective canonical is applied in many contexts to mean "according to the canon" the standard, rule or primary source that is accepted as authoritative for the body of knowledge or literature in that context. In mathematics, "canonical example ...

for

operating system An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...

s that use the

Linux Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, which ...

kernel and the

systemd systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manager ...

init In Unix-based computer operating systems, init (short for ''initialization'') is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down. It is the direct ...

system. The packages, called ''snaps'', and the tool for using them, ''snapd'', work across a range of

Linux distribution A Linux distribution (often abbreviated as distro) is an operating system made from a software collection that includes the Linux kernel and, often, a package management system. Linux users usually obtain their operating system by downloading one ...

s and allow

upstream Upstream may refer to: * Upstream (bioprocess) * ''Upstream'' (film), a 1927 film by John Ford * Upstream (networking) * ''Upstream'' (newspaper), a newspaper covering the oil and gas industry * Upstream (petroleum industry) * Upstream (software ...

software developers to distribute their applications directly to users. Snaps are self-contained applications running in a sandbox with mediated access to the host system. Snap was originally released for

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...

applications but was later ported to also work for

Internet of Things The Internet of things (IoT) describes physical objects (or groups of such objects) with sensors, processing ability, software and other technologies that connect and exchange data with other devices and systems over the Internet or other comm ...

devices and desktop applications.

Functionality

Snap Store

The Snap Store allows developers to publish their snap-packaged applications. All apps uploaded to the Snap Store undergo automatic testing, including a

malware Malware (a portmanteau for ''malicious software'') is any software intentionally designed to cause disruption to a computer, server, client, or computer network, leak private information, gain unauthorized access to information or systems, depri ...

scan. However, the scan does not catch all issues. In one case in May 2018, two applications by the same developer were found to contain a

cryptocurrency A cryptocurrency, crypto-currency, or crypto is a digital currency designed to work as a medium of exchange through a computer network that is not reliant on any central authority, such as a government or bank, to uphold or maintain it. It i ...

miner which ran in the background during application execution. When this issue was found, Canonical removed the applications from the Snap Store and transferred ownership of the Snaps to a trusted third-party which re-published the Snaps without the miner present. Although the Snap sandbox reduces the impact of a malicious app, Canonical recommends users only install Snaps from publishers trusted by the user.

Universal Linux packages

''Snaps'' are

self-contained Self-sustainability and self-sufficiency are overlapping states of being in which a person or organization needs little or no help from, or interaction with, others. Self-sufficiency entails the self being enough (to fulfill needs), and a self-s ...

packages that work across a range of

s. This is unlike traditional Linux package management approaches, which require specifically adapted packages for each Linux distribution. Snap-list

The snap

file format A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file formats ...

is a single compressed

filesystem In computing, file system or filesystem (often abbreviated to fs) is a method and data structure that the operating system uses to control how data is stored and retrieved. Without a file system, data placed in a storage medium would be one larg ...

using the

SquashFS Squashfs is a compressed read-only file system for Linux. Squashfs compresses files, inodes and directories, and supports block sizes from 4 KiB up to 1 MiB for greater compression. Several compression algorithms are supported. Squashfs is al ...

format with the extension .snap. This filesystem contains the application, libraries it depends on, and declarative metadata. This metadata is interpreted by snapd to set up an appropriately shaped secure

sandbox A sandbox is a sandpit, a wide, shallow playground construction to hold sand, often made of wood or plastic. Sandbox or Sand box may also refer to: Arts, entertainment, and media * Sandbox (band), a Canadian rock music group * Sandbox ( ...

for that application. After installation, the snap is mounted by the host operating system and decompressed on the fly when the files are used. Although this has the advantage that snaps use less disk space, it also means some large applications start more slowly. A significant difference between Snap and other universal Linux packaging formats such as

Flatpak Flatpak, formerly known as xdg-app, is a utility for software deployment and package management for Linux. It is advertised as offering a sandbox environment in which users can run application software in isolation from the rest of the system. ...

is that Snap supports any class of Linux application such as desktop applications, server tools, IoT apps and even system services such as the printer driver stack. To ensure this, Snap relies on

for features such as running socket-activated system services in a Snap. This causes Snap to work best only on distributions that can adopt that

init system In Unix-based computer operating systems, init (short for ''initialization'') is the first process started during booting of the computer system. Init is a daemon process that continues running until the system is shut down. It is the direct ...

Configurable sandbox

Applications in a Snap run in a container with limited access to the host system. Using ''Interfaces'', users can give an application mediated access to additional features of the host such as recording audio, accessing USB devices and recording video. These interfaces mediate regular Linux APIs so that applications can function in the sandbox without needing to be rewritten. Desktop applications can also use the XDG Desktop Portals, a standardized API originally created by the

project to give sandboxed desktop applications access to host resources. These portals often provide a better user experience compared to the native Linux APIs because they prompt the user for permission to use resources such as a webcam at the time the application uses them. The downside is that applications and toolkits need to be rewritten in order to use these newer APIs. The Snap sandbox also supports sharing data and Unix sockets between Snaps. This is often used to share common libraries and application frameworks between Snaps to reduce the size of Snaps by avoiding duplication. The Snap sandbox heavily relies on the

AppArmor AppArmor ("Application Armor") is a Linux kernel security module that allows the system administrator to restrict programs' capabilities with per-program profiles. Profiles can allow capabilities like network access, raw socket access, and the ...

Linux Security Module from the upstream

Linux kernel The Linux kernel is a free and open-source, monolithic, modular, multitasking, Unix-like operating system kernel. It was originally authored in 1991 by Linus Torvalds for his i386-based PC, and it was soon adopted as the kernel for the GNU ope ...

. Because only one "major"

Linux Security Module Linux Security Modules (LSM) is a Software framework, framework allowing the Linux kernel to support without bias a variety of computer security models. LSM is licensed under the terms of the GNU General Public License and is a standard part of the ...

(LSM) can be active at the same time, the Snap sandbox is much less secure when another major LSM is enabled. As a result, on distributions such as

Fedora A fedora () is a hat with a soft brim and indented crown.Kilgour, Ruth Edwards (1958). ''A Pageant of Hats Ancient and Modern''. R. M. McBride Company. It is typically creased lengthwise down the crown and "pinched" near the front on both sides ...

which enable

SELinux Security-Enhanced Linux (SELinux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC). SELinux is a set of kernel modifications and user-space t ...

by default, the Snap sandbox is heavily degraded. Although Canonical is working with many other developers and companies to make it possible for multiple LSMs to run at the same time, this solution is still a long time away. The Snap sandbox prevents snapped desktop applications from accessing the themes of the host operating system to prevent compatibility issues. In order for Snaps to use a theme, it also needs to be packaged in a separate Snap. Many popular themes are packaged by the Snap developers but some themes are not supported yet and uncommon themes have to be installed manually. If a theme is not available as a Snap package, users have to resort to choosing the best matching theme available. Work is ongoing to make it easier for third parties to package themes in a Snap and to automatically install uncommon system themes.

Automatic and atomic updates

Multiple times a day, snapd checks for available updates of all Snaps and installs them in the background using an

atomic operation In concurrent programming, an operation (or set of operations) is linearizable if it consists of an ordered list of invocation and response events (event), that may be extended by adding response events such that: # The extended list can be re-e ...

. Updates can be reverted and use

delta encoding Delta encoding is a way of storing or transmitting data in the form of '' differences'' (deltas) between sequential data rather than complete files; more generally this is known as data differencing. Delta encoding is sometimes called delta compre ...

to reduce their download size. Publishers can release and update multiple versions of their software in parallel using ''channels''. Each channel has a specific ''track'' and ''risk'', which indicate the ''version'' and ''stability'' of the software released on that channel. When installing an application, Snap defaults to using the latest/stable channel, which will automatically update to new major releases of the software when they become available. Publishers can create additional channels to give users the possibility to stick to specific major releases of their software. For example, a 2.0/stable channel would allow users to stick to the 2.0 version of the software and only get minor updates without the risk of backwards incompatible changes. When the publisher releases a new major version in a new channel, users can manually update to the next version when they choose. The schedule, frequency and timing of automatic updates can be configured by users. For example, this command will check for updates on the last Friday from 23:00 to 01:00. $ sudo snap set system refresh.timer=fri5,23:00-01:00 Users can also pause automatic updates for a certain period of time, or indefinitely. Updates are automatically paused on metered connections.

Snapcraft

Snapcraft is a tool for developers to package their programs in the Snap format. It runs on any Linux distribution supported by Snap,

macOS macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and lapt ...

and

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for serv ...

. Snapcraft builds the packages in a

Virtual Machine In computing, a virtual machine (VM) is the virtualization/emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardw ...

using Multipass, in order to ensure the result of a build is the same, regardless of which distribution or operating system it is built on. Snapcraft supports multiple build tools and programming languages, such as Go,

Java Java (; id, Jawa, ; jv, ꦗꦮ; su, ) is one of the Greater Sunda Islands in Indonesia. It is bordered by the Indian Ocean to the south and the Java Sea to the north. With a population of 151.6 million people, Java is the world's List ...

JavaScript JavaScript (), often abbreviated as JS, is a programming language that is one of the core technologies of the World Wide Web, alongside HTML and CSS. As of 2022, 98% of Website, websites use JavaScript on the Client (computing), client side ...

Python Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

, C/

C++ C++ (pronounced "C plus plus") is a high-level general-purpose programming language created by Danish computer scientist Bjarne Stroustrup as an extension of the C programming language, or "C with Classes". The language has expanded significan ...

and

Rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO(OH ...

. It also allows importing application metadata from multiple sources such as

AppStream AppStream is an agreement between major Linux vendors (i.e. Red Hat, Canonical, SUSE, Debian, Mandriva, etc.) to create an infrastructure for application installers on Linux and sharing of metadata. The initiative was started as early as 19-21 Ja ...

git Git () is a distributed version control system: tracking changes in any set of files, usually used for coordinating work among programmers collaboratively developing source code during software development. Its goals include speed, data inte ...

, shell scripts and setup.py files.

Adoption

Snap initially only supported the all-Snap Ubuntu Core distribution, but in June 2016, it was ported to a wide range of Linux distributions to become a format for universal Linux packages. Snap requires

Systemd systemd is a software suite that provides an array of system components for Linux operating systems. Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manager ...

which is available in most, but not all, Linux distributions. Other

Unix-like A Unix-like (sometimes referred to as UN*X or *nix) operating system is one that behaves in a manner similar to a Unix system, although not necessarily conforming to or being certified to any version of the Single UNIX Specification. A Unix-li ...

systems (e.g.

FreeBSD FreeBSD is a free and open-source Unix-like operating system descended from the Berkeley Software Distribution (BSD), which was based on Research Unix. The first version of FreeBSD was released in 1993. In 2005, FreeBSD was the most popular ...

) are not supported.

ChromeOS ChromeOS, sometimes stylized as chromeOS and formerly styled as Chrome OS, is a Linux-based operating system designed by Google. It is derived from the open-source ChromiumOS and uses the Google Chrome web browser as its principal user interfac ...

does not support Snap directly, only through Linux distros installed in it that support Snap, such as Gallium OS. A number of Linux distributions support Snap out of the box such as

Ubuntu Ubuntu ( ) is a Linux distribution based on Debian and composed mostly of free and open-source software. Ubuntu is officially released in three editions: ''Desktop'', ''Server'', and ''Core'' for Internet of things devices and robots. All the ...

(and its derivatives, such as

Kubuntu Kubuntu ( ) is an official flavor of the Ubuntu operating system that uses the KDE Plasma Desktop instead of the GNOME desktop environment. As part of the Ubuntu project, Kubuntu uses the same underlying systems. Kubuntu shares the same repositor ...

and

Xubuntu Xubuntu () is a Canonical Ltd.–recognized, community-maintained derivative of the Ubuntu operating system. The name ''Xubuntu'' is a portmanteau of ''Xfce'' and ''Ubuntu'', as it uses the Xfce desktop environment, instead of Ubuntu's Unity a ...

Manjaro Manjaro ( ) is a free and open-source Linux distribution based on the Arch Linux operating system that has a focus on user-friendliness and accessibility. It uses a rolling release update model and Pacman as its package manager. It is developed ...

Zorin OS Zorin may refer to: People * Andrei Zorin (born 1997), Russian footballer * Leonid Zorin, (1924–2020), Russian playwright * Sergey Zorin (1891–1937), Soviet politician * Simcha Zorin (1902–1974), Soviet Jewish partisan in World War II * Valen ...

, KDE Neon,

Solus Solus may refer to: *Solus or Soluntum, an ancient city of Sicily * ''Solus'' (comics), an American comic book series *Solus (operating system), an operating system based on the Linux kernel * ''Solus'' (moth), a genus of moths in the family Saturn ...

and Li-f-e. Snap is also available for many other distributions such as

CentOS CentOS (, from Community Enterprise Operating System; also known as CentOS Linux) is a Linux distribution that provides a free and open-source community-supported computing platform, functionally compatible with its upstream source, Red Hat En ...

Debian Debian (), also known as Debian GNU/Linux, is a Linux distribution composed of free and open-source software, developed by the community-supported Debian Project, which was established by Ian Murdock on August 16, 1993. The first version of D ...

Elementary OS elementary OS is a Linux distribution based on Ubuntu LTS. It promotes itself as a "thoughtful, capable, and ethical" replacement to macOS and Windows and has a pay-what-you-want model. The operating system, the desktop environment (called P ...

, GalliumOS,

Kali Linux Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. It is maintained and funded by Offensive Security. Kali Linux has around 600 penetration-testing programs (tools), including Armitage (a gr ...

Linux Mint Linux Mint is a community-driven Linux distribution based on Ubuntu (which is in turn based on Debian), bundled with a variety of free and open-source applications. It can provide full out-of-the-box multimedia support for those who choose to i ...

OpenEmbedded OpenEmbedded is a build automation framework and cross-compile environment used to create Linux distributions for embedded devices. The OpenEmbedded framework is developed by the OpenEmbedded community, which was formally established in 2003. Ope ...

Parrot Security OS Parrot OS is a Linux distribution based on Debian with a focus on security, privacy, and development. Core Parrot is based on Debian's "testing" branch, with a Linux 5.10 kernel. It follows a rolling release development model. The desktop ...

Pop!_OS Pop!_OS is a free and open-source Linux distribution, based upon Ubuntu, and featuring a customized GNOME desktop environment known as COSMIC. The distribution is developed by American Linux computer manufacturer System76. Pop!_OS is primarily ...

Raspbian Raspberry Pi OS (formerly Raspbian) is a Unix-like operating system based on the Debian Linux distribution for the Raspberry Pi family of compact single-board computers. First developed independently in 2012, it has been produced as the primary o ...

Red Hat Enterprise Linux Red Hat Enterprise Linux (RHEL) is a commercial open-source Linux distribution developed by Red Hat for the commercial market. Red Hat Enterprise Linux is released in server versions for x86-64, Power ISA, ARM64, and IBM Z and a desktop version ...

and

openSUSE openSUSE () is a free and open-source software, free and open source RPM Package Manager, RPM-based Linux distribution developed by the openSUSE project. The initial release of the community project was a beta version of SUSE Linux 10.0. Addi ...

. A number of notable Desktop software development companies publish their software in the Snap Store, including

Google Google LLC () is an American multinational technology company focusing on search engine technology, online advertising, cloud computing, computer software, quantum computing, e-commerce, artificial intelligence, and consumer electronics. ...

JetBrains JetBrains s.r.o. (formerly IntelliJ Software s.r.o.) is a Czech software development company which makes tools for software developers and project managers. , the company has offices in Prague; Munich; Berlin; Boston, Massachusetts; Amsterda ...

KDE KDE is an international Free software movement, free software community that develops free and open-source software. As a central development hub, it provides tools and resources that allow collaborative work on this kind of software. Well-know ...

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

(for Linux versions of e.g. .NET Core 3.1,

Visual Studio Code Visual Studio Code, also commonly referred to as VS Code, is a source-code editor made by Microsoft with the Electron Framework, for Windows, Linux and macOS. Features include support for debugging, syntax highlighting, intelligent code complet ...

Skype Skype () is a proprietary telecommunications application operated by Skype Technologies, a division of Microsoft, best known for VoIP-based videotelephony, videoconferencing and voice calls. It also has instant messaging, file transfer, deb ...

, and

PowerShell PowerShell is a task automation and configuration management program from Microsoft, consisting of a command-line shell (computing), shell and the associated scripting language. Initially a Windows component only, known as Windows PowerShell, it ...

Mozilla Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, wi ...

and

Spotify Spotify (; ) is a proprietary Swedish audio streaming and media services provider founded on 23 April 2006 by Daniel Ek and Martin Lorentzon. It is one of the largest music streaming service providers, with over 456 million monthly active us ...

. Snaps are also used in Internet-of-Things environments, ranging from consumer-facing products to enterprise device management gateways and

satellite communication A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. C ...

networks. Finally, Snap is also used by developers of server applications such as

InfluxDB InfluxDB is an open-source time series database (TSDB) developed by the company InfluxData. It is written in the Go programming language for storage and retrieval of time series data in fields such as operations monitoring, application metr ...

, Kata Containers,

Nextcloud Nextcloud is a suite of client-server software for creating and using file hosting services. Nextcloud provides functionally similar to Dropbox, Office 365 or Google Drive when used with integrated office suite solutions Collabora Online or Only ...

and

Travis CI Travis CI is a hosted continuous integration service used to build and test software projects hosted on GitHub, Bitbucket, GitLab, Perforce, Apache Subversion and Assembla. Travis CI was the first CI service that provided services to open-sourc ...

. In 2019, Canonical decided to switch the Chromium web browser in future Ubuntu releases from an APT package to a Snap. They explained that Snap made it much easier to support Chromium on all supported Ubuntu releases. This allowed them to focus engineering resources on other parts of the Ubuntu desktop. As a result of this decision, Ubuntu derivatives such as Linux Mint had to choose between maintaining their own version of the Chromium package or switching to the snapped version of Chromium maintained by Canonical.

Reception

Snap has received mixed reaction from the developer community. On Snap's promotional site,

Heroku Heroku is a cloud platform as a service (PaaS) supporting several programming languages. One of the first cloud platforms, Heroku has been in development since June 2007, when it supported only the Ruby programming language, but now supports Java, ...

praised Snap's auto-update as it fits their fast release schedule well.

mentions its ease of use and Snap being

YAML YAML ( and ) (''see '') is a human-readable data-serialization language. It is commonly used for configuration files and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as Exte ...

-based, as well as it being distribution-agnostic.

says the Snap Store gives their tools more exposure. Others have objected to the closed-source nature of the Snap Store. Clement Lefebvre (

founder and project leader) has written that Snap is biased and has a conflict of interest. The reasons he cited include it being governed by Canonical and locked to their store, and also that Snap works better on Ubuntu than on other distributions. He later announced that the installing of Snap would be blocked by

APT Apt. is an abbreviation for apartment. Apt may also refer to: Places * Apt Cathedral, a former cathedral, and national monument of France, in the town of Apt in Provence * Apt, Vaucluse, a commune of the Vaucluse département of France * A ...

in Linux Mint, although a way to disable this restriction would be documented.

References

External links

Official website

A technical comparison between snaps and debs
{{Linux package management systems Free software Linux installation software Linux package management-related software Operating system technology Package management systems Software distribution Ubuntu