What is snap in linux

Snap documentation

Snaps are Linux app packages for desktop, cloud and IoT that are simple to install, secure, cross-platform, and dependency-free.

They update automatically and typically run within a confined and transaction-based environment. Security and robustness are their key features, alongside being easy to install, easy to maintain and easy to upgrade.

Snaps help desktop users effortlessly install and run apps like Spotify or Slack. They help sysadmins run servers like NextCloud, developers to package and distribute their work to the global Snap Store, and they help everyone build and deploy IoT devices running Ubuntu Core.

From Linux and maker space tinkerers, to the robotics, automotive and signage industries; from your desktop to a deployment of thousands, snap can handle it.

Creating your own snap?

In this documentation

Tutorials Get started — a hands-on introduction to using snap packages for new users	How-to guides Step-by-step guides covering key operations and common tasks
Reference Technical information — specifications, APIs, architecture	Explanation Concepts — discussion and clarification of key topics

Project and community

Snap and Snapcraft are members of the Ubuntu family. They’re both open source projects that welcome community involvement, contributions, suggestions, fixes and constructive feedback.

Thinking about using snap for your next project? Get in touch!

Last updated 2 days ago.

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Snap

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, distribution-agnostic upstream software deployment. Canonical, the developer of Snap, manages the Snap Store service through which snaps are deployed.

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.

• If AppArmor is not enabled in your system then all snaps will run in devel mode which mean they will have the same unrestricted access to your system as apps installed from Arch Linux repositories.
• Running untrusted code is never safe, sandboxing cannot change this.

Installation

Tip: snapd installs a script in /etc/profile.d/snapd.sh to export the paths of binaries installed with the snapd package and desktop entries. Reboot once to make this change take effect.

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, enable/start 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:

$ snap find searchterm 

Installing

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

# snap install snapname 

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:

# snap install --dangerous /path/to/snap 

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:

# snap set core refresh.timer=0:00~24:00/2

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

Removing

Snaps can be removed by executing:

# snap remove snapname 

Tips and tricks

Classic snaps

Some snaps (e.g. Julia 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:

# ln -s /var/lib/snapd/snap /snap

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:

Hello Evil World! This example demonstrates the app confinement You should see a permission denied error next /snap/hello-world/27/bin/evil: 9: /snap/hello-world/27/bin/evil: cannot create /var/tmp/myevil.txt: Permission denied

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

. [ +0.000003] audit: type=1327 audit(1540469583.966:257): proctitle=2F62696E2F7368002F736E61702F68656C6C6F2D776F726C642F32372F62696E2F6576696C [ +12.268939] audit: type=1400 audit(1540469596.236:258): apparmor="DENIED" operation="open" profile="snap.hello-world.evil" name="/var/tmp/myevil.txt" pid=10835 comm="evil" requested_mask="wc" denied_mask="wc" fsuid=1000 ouid=1000 [ +0.000006] audit: type=1300 audit(1540469596.236:258): arch=c000003e syscall=2 success=no exit=-13 a0=55d991ba6bc8 a1=241 a2=1b6 a3=55d991ba6be0 items=0 ppid=31349 pid=10835 auid=1000 uid=1000 gid=1000 euid=1000 suid=1000 fsuid=1000 egid=1000 sgid=1000 fsgid=1000 tty=pts2 ses=3 comm="evil" exe="/bin/dash" subj==snap.hello-world.evil (enforce) .

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

# aa-status | grep snap.hello-world

snap.hello-world.env snap.hello-world.evil snap.hello-world.hello-world snap.hello-world.sh

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

$ snap debug sandbox-features

apparmor: kernel:caps kernel:domain kernel:file kernel:mount kernel:namespaces kernel:network_v8 kernel:policy kernel:ptrace kernel:query kernel:rlimit kernel:signal parser:unsafe policy:default support-level:partial confinement-options: devmode dbus: mediated-bus-access kmod: mediated-modprobe mount: freezer-cgroup-v1 layouts mount-namespace per-snap-persistency per-snap-profiles per-snap-updates per-snap-user-profiles stale-base-invalidation seccomp: bpf-argument-filtering kernel:allow kernel:errno kernel:kill_process kernel:kill_thread kernel:log kernel:trace kernel:trap

Hide the snap folder

Troubleshooting

Text unreadable

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

# rm -f /var/cache/fontconfig/* $ rm -f ~/.cache/fontconfig/* # fc-cache -r -v

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

$ find ~/snap/ -wholename '*/.cache/fontconfig'

. /home/darth_vader/snap/mailspring/common/.cache/fontconfig . /home/darth_vader/snap/authy/common/.cache/fontconfig . /home/darth_vader/snap/icedrive/common/.cache/fontconfig . /home/darth_vader/snap/discord/common/.cache/fontconfig . /home/darth_vader/snap/bitwarden/common/.cache/fontconfig

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:

error: system does not fully support snapd: cannot mount squashfs image using "squashfs"

you may verify that the SquashFS kernel module is loaded with

Module Size Used by squashfs xxxxx x .

Tip: If you have recently installed the snapd package to your system, you may need to reboot Arch Linux before installing Snap packages.

Graphical management

The factual accuracy of this article or section is disputed.

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

The Snap Store can be installed via snap

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.

See also

• Official site
• GitHub repository
• ArsTechnica article (2016-06) about Ubuntu snaps becoming available for Arch and other distributions

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What Are Snaps? And How Are They Important?

With the upcoming release of Ubuntu 17.04 in April, names like Ubuntu Snaps and Unity 8 have frequently been mentioned. Most developers understand what the fuzz is about, but that’s probably not the case for Linux newbies.

So, today, we will briefly touch on what Snaps; are, how they are important, and whether to be excited about this new development or not.

What are Snaps?

Snaps are ultimately applications compressed together with their dependencies and descriptions of how to run and interact with other software on the system you installed it on.

They are mainly designed to be sandboxed and isolated from other system software, secure, and easily installable, upgradeable, degradable, and removable irrespective of its underlying system.

Canonical is developing Snaps as the new packaging medium for Ubuntu’s Internet of Things devices and large container deployments referred to as Ubuntu Core.

Features of Snaps

Snaps features provide it a significant contribution to the Linux community as, to quote Canonical, they give developers the ability to

package any app for every Linux desktop, server, cloud or device, and deliver updates directly.

Below are highlights of why Snaps are excellent:

Affordability

Get up and running with Snaps free of charge and start building your apps right on Ubuntu Core.

Portability

Snaps allow you to develop, package, install and update your apps on any Linux desktop, cloud, and server with one swoop.

No more searching for the ways to install the same apps on different Linux distros, especially since many other distros are validating the new tech.

Faster Installations and Upgrades

With Snaps installing and upgrading applications will be a breeze because all the dependencies are already present in the zip file so no more broken apps.

Support from Community

As is the case with Ubuntu, so it is with Snaps and Ubuntu Core. Know that you have the backing of a vast developer community to help you out whenever you get stuck as a developer or as a Linux enthusiast implementing Snaps.

How to Install Snap in Linux

In this section, I will show you to install Snap in Linux and how to use snap to install, update or remove packages.

Since Ubuntu 16.04, Snap is already pre-installed on the system, so we don’t need to install again. For other distribution, you can follow instructions as shown:

On Arch Linux

$ sudo yaourt -S snapd $ sudo systemctl start snapd.socket

On Fedora

$ sudo dnf copr enable zyga/snapcore $ sudo dnf install snapd $ sudo systemctl enable --now snapd.service $ sudo setenforce 0

Once snap has been installed and started, you can list all available packages in the snap store as shown.

To search for a particular package, just specify package name as show.

To install a snap package, specifying the package by name.

$ sudo snap install package-name

To update an installed snap package, specifying the package by name.

$ sudo snap refresh package-name

To remove an installed snap package, run.

$ sudo snap remove package-name

To learn more about snap packages, go through the man pages or follow below links.

Learn More about Snaps, Ubuntu Core, and Ubuntu IoT

You are welcome to find out more about Snaps by checking out the resources below:

I hope you have been able to get at least, a fundamental understanding of what Snaps are and why they are a big deal to the Linux community. Feel free to drop your comments below and to also make suggestions of information I might have left out.

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