Docker

2022-04-21T07:55:22Z

Arp242: /* Grub */ seems some stuff got lost here

== Installation ==

The Docker package is in the 'Community' repository. See [[Alpine_Linux_package_management]] how to add a repository.

apk add docker

Connecting to the Docker daemon through its socket requires you to add yourself to the `docker` group.

addgroup username docker

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

rc-update add docker boot
service docker start

{{Note|On older versions of Alpine Linux with older versions of docker you'll also need to disable some kernel security flags in order to build images:}}

sysctl -w kernel.grsecurity.chroot_deny_chmod=0
sysctl -w kernel.grsecurity.chroot_deny_mknod=0

For more information, have a look at the [https://github.com/docker/docker/issues/20303 corresponding Github issue].

This weakening of security is not necessary to do with Alpine 3.4.x and Docker 1.12 as of August 2016.

=== Docker Compose ===

'docker-compose' is in the 'Community' repository starting with Alpine Linux 3.10.

apk add docker-compose

For older releases:

'''To install docker-compose, first install pip:'''

apk add py-pip python3-dev libffi-dev openssl-dev gcc libc-dev make
pip3 install docker-compose</code>

== 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 '''/etc/docker/daemon.json'''

<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 here[https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file].

== 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 config 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''' ==

The best documentation on using Docker and creating containers is at the main docker site. Adding anything to it here would be redundant.

'''http://docs.docker.com/'''

If you create an account at docker.com, you can browse through user images and learn from the syntax in contributed dockerfiles.

Official Docker image files are denoted on the website by a blue ribbon.

== 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