Docker

2019-04-05T13:19:41Z

Ruluk: /* Installation */ Docker-compose requires new dependencies in latest version. See https://github.com/docker/compose/issues/6617#issuecomment-477974325.

Alpine makes a great docker container, because it is so small and optimized to be run in RAM.
It might also might make a good controller for several docker containers with enough RAM. I haven't tested this yet
Docker's setup is easy to use from command line. Commands can be run from an interactive shell, or through a configuration file called a "Dockerfile".
docker.com has excellent walk-throughs on how to run, pull, setup a container, commit an image, and create a configuration file. hub.docker.com is a freemium setup, where the first private repository is free.

== Installation ==

Run <code>apk add docker</code> to install Docker on Alpine Linux.

The Docker package is in the 'Community' repository, so if the '''apk add''' fails with '''unsatisfiable constraints''', you need to edit the '''/etc/apk/repositories''' file to add (or uncomment) a line like:

<code>http://dl-cdn.alpinelinux.org/alpine/latest-stable/community</code>

then run <code>apk update</code> to index the repository.

'''To start the Docker daemon at boot, run:'''

<code>rc-update add docker boot</code>

'''Then to start the Docker daemon manually, run:'''

<code>service docker start</code>

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

<code>sysctl -w kernel.grsecurity.chroot_deny_chmod=0</code>

<code>sysctl -w kernel.grsecurity.chroot_deny_mknod=0</code>

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

Anyway, this weakening of security is not necessary to do with Alpine 3.4.x and Docker 1.12 as of August 2016 anymore.

=== Docker Compose ===

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

<code>apk add py-pip</code>

'''Since docker-compose version 1.24.0, you also need some dev dependencies:'''

<code>apk add python-dev libffi-dev openssl-dev gcc libc-dev make</code>

'''Then install docker-compose, run:'''

<code>pip 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>

and add in '''/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 will 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 may, probably, encounter this message by executing <code>docker info</code>.
To correct this situation we have to enable the <code>cgroup_enable=memory swapaccount=1</code>

==== Alpine 3.8 ====
Well I'm not sure it was'nt the case before but for sure with Alpine 3.8 you must config cgroups properly
<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 ===
Well; if you use Grub it is like any other linux and you just have to add the cgroup condition into <code>/etc/default/grub</code> than upgrade your grub

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

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

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

than update the config and reboot

<code>update-extlinux</code>

== '''How to use docker''' ==

The best documentation for how to use Docker and create containers is at the main docker site. Adding anything more to it here would be redundant.

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

if you create an account at docker.com you can browse through other user's images and learn from the syntax in contributor's dockerfiles.

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

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

[[Category:Virtualization]]

Alpine Linux - User contributions [en]

Docker