In this guide, I’ll take you through the steps to install and use snapd service on CentOS 7 server. For those new to snap terminology, snap comes from Snappy which is a package management and software deployment system from Canonical. It was originally designed for the Ubuntu phone operating system.
What is a snap?
- is a squashFS filesystem containing your app code and a
snap.yamlfile containing specific metadata. It has a read-only file-system and, once installed, a writable area.
- is self-contained. It bundles most of the libraries and runtimes it needs and can be updated and reverted without affecting the rest of the system.
- is confined from the OS and other apps through security mechanisms, but can exchange content and functions with other snaps according to fine-grained policies controlled by the user and the OS defaults.
What is Snapd?
Snapd is a REST API daemon service that runs on your Linux system to manage snap packages (“snaps“). It interacts with the snap store and provides the command client
snap used to interact with it. You must install snapd before you can start managing snaps on any Linux distribution.
Why use Snaps?
Snap packages any app for every Linux desktop, server, cloud or device. Snaps are faster to install, easier to create, safer to run, and they update automatically and transactionally so your app is always fresh and never broken. You can bring your own build infrastructure or use ours.
How to Install and Use Snapd on CentOS 7
Follow steps below to install Snapd on CentOS 7 server.
Step 1: Install the COPR plugin and EPEL
Kick off the installation by adding
epel repository and installing
copr yum plugin.
sudo yum install epel-release sudo yum install yum-plugin-copr
Then add the repo:
$ sudo yum copr enable ngompa/snapcore-el7 Loaded plugins: copr, fastestmirror You are about to enable a Copr repository. Please note that this repository is not part of the main Fedora distribution, and quality may vary. The Fedora Project does not exercise any power over the contents of this repository beyond the rules outlined in the Copr FAQ at <https://fedorahosted.org/copr/wiki/UserDocs#WhatIcanbuildinCopr>, and packages are not held to any quality or securty level. Please do not file bug reports about these packages in Fedora Bugzilla. In case of problems, contact the owner of this repository. Do you want to continue? [y/N]: y copr done
Once the repository has been added, install snapd package.
sudo yum -y install snapd
Wait for the installation to finish then enable snapd socket:
$ sudo systemctl enable --now snapd.socket Created symlink from /etc/systemd/system/sockets.target.wants/snapd.socket to /usr/lib/systemd/system/snapd.socket.
Classic confinement requires snaps under
/snap or symlink from
/var/lib/snapd/snap. Create a symlink for it like below:
sudo ln -s /var/lib/snapd/snap /snap
Snapd is now ready for use. You interact with it using the snap command. See help page below:
# snap --help Usage: snap [OPTIONS] <command> Install, configure, refresh and remove snap packages. Snaps are 'universal' packages that work across many different Linux systems, enabling secure distribution of the latest apps and utilities for cloud, servers, desktops and the internet of things. This is the CLI for snapd, a background service that takes care of snaps on the system. Start with 'snap list' to see installed snaps. Application Options: --version Print the version and exit Help Options: -h, --help Show this help message Available commands: abort Abort a pending change ack Adds an assertion to the system alias Sets up a manual alias aliases Lists aliases in the system buy Buys a snap changes List system changes connect Connects a plug to a slot disable Disables a snap in the system disconnect Disconnects a plug from a slot download Downloads the given snap enable Enables a snap in the system find Finds packages to install (aliases: search) get Prints configuration options help Help info show detailed information about a snap install Installs a snap to the system interface Lists snap interfaces interfaces Lists interfaces in the system known Shows known assertions of the provided type list List installed snaps login Authenticates on snapd and the store logout Log out of the store logs Retrieve logs of services pack pack the given target dir as a snap prefer Prefer aliases from a snap and disable conflicts refresh Refreshes a snap in the system remove Removes a snap from the system restart Restart services revert Reverts the given snap to the previous state run Run the given snap command services Query the status of services set Changes configuration options start Start services stop Stop services switch Switches snap to a different channel tasks List a change's tasks (aliases: change) try Tests a snap in the system unalias Unalias a manual alias or an entire snap version Shows version details watch Watch a change in progress whoami Prints the email the user is logged in with.
How to Install Snap Applications on CentOS 7
snap command line tool to interact with snaps available on Snap Store.
Searching for a snap:
To search for Snaps, use
$ snap find <search terms>
This will query the store and list the results with their version number, developer names, and the description.
I’ll do an example for installation of Microsoft PowerShell automation and configuration management platform on CentOS 7 server.
# snap search powershell Name Version Developer Notes Summary powershell-preview 6.1.0-preview.4 microsoft-powershell classic PowerShell for every system! powershell 6.0.4 microsoft-powershell classic PowerShell for every system!
Install snap by running:
sudo yum install -y icu sudo snap install powershell --classic
Wait for the download to finish, it should take short time to complete. Since the binary file is located under,
/snap/bin/ we need to add this to the
$ sudo vim /etc/profile export PATH="$PATH:/snap/bin/"
Source the file to get new PATH
Test by starting the
# pwsh PowerShell v6.0.4 Copyright (c) Microsoft Corporation. All rights reserved. https://aka.ms/pscore6-docs Type 'help' to get help. PS /root>
To list installed snaps:
# snap list Name Version Rev Developer Notes core 16-2.34.3 5145 canonical core powershell 6.0.4 8 microsoft-powershell classic
Manually update snaps by running
# snap refresh powershell snap "powershell" has no updates available
To remove a snap, all you need to do is run.
snap remove <snap name> In our case just do:
# snap remove powershell powershell removed
Check snap info:
Use the command
snap info to check for more info about a snap package.
[[email protected] ~]# snap info powershell name: powershell summary: PowerShell for every system! publisher: microsoft-powershell contact: https://github.com/powershell/powershell description: | PowerShell is an automation and configuration management platform. It consists of a cross-platform (Windows, Linux, and macOS) command-line shell and associated scripting language. See https://docs.microsoft.com/en-us/powershell/scripting/powershell-core-support for support details. snap-id: JSNnoJl3EqkMuWoy5Dgq8PMqZ0uNcpie channels: stable: 6.0.4 (8) 58MB classic candidate: 6.0.4 (8) 58MB classic beta: 6.0.4 (8) 58MB classic edge: 6.0.4 (8) 58MB classic
Roll back to a previous version of an application
$ sudo snap revert <snap name>
By now you should be able to install snaps the store, manually update them, remove them, check installed snaps and much more. The snap command line is designed to be as simple and memorisable as possible. It should become a second nature to you after using it just a couple of times.
Another example which uses a snap for installation is How to Install Wekan Open source Kanban on CentOS 7 with Nginx and Letsencrypt SSL.