Docker

2024-08-28T23:44:50Z

TokyoStarz: make addgroup command copy and pastable

== Installation ==

The {{Pkg|docker}} package is in the ''community'' repository. See [[Repositories]] how to add a repository.

apk add docker

Connecting to the Docker daemon through its socket requires you to add yourself to the <code>docker</code> group.

addgroup ${USER} docker

To start the Docker daemon at boot, see [[OpenRC]].

rc-update add docker default
service docker start

=== Docker rootless ===

Docker rootless allows unprivileged users to run the docker daemon and docker containers in user namespaces. This is not the same as dockremap explained in the section below. With dockremap the daemon still runs as root.

This requires the {{Pkg|docker-rootless-extras}} package (available in ''community'') and enabling <code>cgroups v2</code>:
edit <code>/etc/rc.conf</code> and set <code>rc_cgroup_mode="unified"</code>. Then start the service on boot:

rc-update add cgroups

Additionally, the <code>/etc/subuid</code> and <code>/etc/subgid</code> files need to be set up as explained in [https://docs.docker.com/engine/security/rootless/ the official documentation].

=== Docker Compose ===

{{Pkg|docker-cli-compose}} is in the ''community'' repository starting with Alpine Linux 3.15.

apk add docker-cli-compose

== Isolate containers with a user namespace ==
<pre>
adduser -SDHs /sbin/nologin dockremap
addgroup -S dockremap
echo dockremap:$(cat /etc/passwd|grep dockremap|cut -d: -f3):65536 >> /etc/subuid
echo dockremap:$(cat /etc/passwd|grep dockremap|cut -d: -f4):65536 >> /etc/subgid
</pre>

add to <code>/etc/docker/daemon.json</code>

<pre>
{
"userns-remap": "dockremap"
}
</pre>

''You may also consider these options : ''
"experimental": false,
"live-restore": true,
"ipv6": false,
"icc": false,
"no-new-privileges": false'''''

You'll find all possible configurations [https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file here].

== Example: How to install docker from Arch ==

https://wiki.archlinux.org/index.php/Docker

== "WARNING: No {swap,memory} limit support" ==

You might encounter this message when executing <code>docker info</code>.
To correct this situation, we have to enable the <code>cgroup_enable=memory swapaccount=1</code>

==== Alpine 3.8 ====
It may not have been the case before, but with Alpine 3.8, you must configure cgroups properly

{{Warning|This seems ''not'' to work with Alpine 3.9 and Docker 18.06. Follow the instructions for grub or extlinux below instead.}}

<pre>echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab</pre>
<pre>
cat >> /etc/cgconfig.conf <<EOF
mount {
cpuacct = /cgroup/cpuacct;
memory = /cgroup/memory;
devices = /cgroup/devices;
freezer = /cgroup/freezer;
net_cls = /cgroup/net_cls;
blkio = /cgroup/blkio;
cpuset = /cgroup/cpuset;
cpu = /cgroup/cpu;
}
EOF
</pre>

=== Grub ===
If you use Grub, add the cgroup condition into <code>/etc/default/grub</code>, then upgrade your grub

<pre>GRUB_CMDLINE_LINUX_DEFAULT="... cgroup_enable=memory swapaccount=1"</pre>

=== Extlinux ===
With Extlinux, you add the cgroup condition, but inside of <code>/etc/update-extlinux.conf</code>

<pre>default_kernel_opts="... cgroup_enable=memory swapaccount=1"</pre>

then update the config and reboot

<code>update-extlinux</code>

== How to use docker ==

Check the [https://docs.docker.com/ official documentation] for details on general usage of docker, including creating and management of containers. Repeating these instructions here be redundant.

Public images can be browsed at the [https://hub.docker.com/ Docker Hub]. These should also serve as further reference on the Dockerfile format.

Official Docker image files are denoted on the website by a special badge.

== See also ==
* [https://www.erianna.com/creating-a-alpine-linux-repository/ Creating and Hosting an Alpine Linux Package Repository for Docker Packages]
* [[Running Alpine in a Docker Container]]

[[Category:Virtualization]]

Alpine Linux - User contributions [en]

Docker