Docker: Difference between revisions

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Alpine makes a great docker container, because it is so small and optimized to be run in RAM.
== Installation ==
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 ==
The {{Pkg|docker}} package is in the ''community'' repository. See [[Repositories]] how to add a repository.
   
 
Run <code>apk add docker</code> to install Docker on Alpine Linux.
  apk add docker
 
Connecting to the Docker daemon through its socket requires you to add yourself to the <code>docker</code> group.


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:
addgroup ${USER} docker


<code>http://dl-cdn.alpinelinux.org/alpine/edge/community</code>
To start the Docker daemon at boot, see [[OpenRC]].


then run <code>apk update</code> to index the repository.
rc-update add docker default
service docker start


=== Docker rootless ===


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


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


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


<code>service docker start</code>
=== Docker Compose ===


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


{{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:}}
apk add docker-cli-compose


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


<code>sysctl -w kernel.grsecurity.chroot_deny_mknod=0</code>
add to <code>/etc/docker/daemon.json</code>


For more information, have a look at the [https://github.com/docker/docker/issues/20303 corresponding Github issue].
<pre>
{ 
        "userns-remap": "dockremap"
}
</pre>


Anyway, this weakening of security is not necessary to do with Alpine 3.4.x and Docker 1.12 as of August 2016 anymore.
''You may also consider these options : ''
        "experimental": false,
        "live-restore": true,
        "ipv6": false,
        "icc": false,
        "no-new-privileges": false'''''


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


'''To install docker-compose, first install pip:'''
== Example: How to install docker from Arch ==


<code>apk add py-pip</code>
https://wiki.archlinux.org/index.php/Docker


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


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


<code>pip install docker-compose</code>
==== Alpine 3.8 ====
It may not have been the case before, but with Alpine 3.8, you must configure cgroups properly


== Isolate containers with a user namespace ==
{{Warning|This seems ''not'' to work with Alpine 3.9 and Docker 18.06. Follow the instructions for grub or extlinux below instead.}}
{{Note|Probably not the best way to do it but it work}}


<pre>echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab</pre>
<pre>
<pre>
adduser -DHs dockremap}}
cat >> /etc/cgconfig.conf <<EOF
echo dockremap:$(cat /etc/passwd\|grep dockremap\|cut -d: -f3):65536 >> /etc/subuid
mount {
echo dockremap:$(cat /etc/passwd\|grep dockremap\|cut -d: -f4):65536 >> /etc/subgid
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>
</pre>


{{Cmd|vi /etc/init.d/docker}}
=== Grub ===
<pre>
If you use Grub, add the cgroup condition into <code>/etc/default/grub</code>, then upgrade your grub
command_args="-p \"${pidfile}\" ${DOCKER_OPTS} --userns-remap=default"
 
</pre>
<pre>GRUB_CMDLINE_LINUX_DEFAULT="... cgroup_enable=memory swapaccount=1"</pre>


''If i may recommend you, you should add also : '''--icc=false --no-new-security'''''
=== Extlinux ===
With Extlinux, you add the cgroup condition, but inside of <code>/etc/update-extlinux.conf</code>


== Example: How to install docker from Arch ==
<pre>default_kernel_opts="... cgroup_enable=memory swapaccount=1"</pre>


https://wiki.archlinux.org/index.php/Docker
then update the config and reboot


== '''How to use docker''' ==
<code>update-extlinux</code>


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.
== How to use docker ==


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


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


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

Latest revision as of 23:44, 28 August 2024

Installation

The 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 docker 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 docker-rootless-extras package (available in community) and enabling cgroups v2: edit /etc/rc.conf and set rc_cgroup_mode="unified". Then start the service on boot: 

rc-update add cgroups

Additionally, the /etc/subuid and /etc/subgid files need to be set up as explained in the official documentation.

Docker Compose

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

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

add to /etc/docker/daemon.json 

{  
        "userns-remap": "dockremap"
}

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.

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 docker info. To correct this situation, we have to enable the cgroup_enable=memory swapaccount=1

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.


echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab
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

Grub

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

GRUB_CMDLINE_LINUX_DEFAULT="... cgroup_enable=memory swapaccount=1"

Extlinux

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

default_kernel_opts="... cgroup_enable=memory swapaccount=1"

then update the config and reboot

update-extlinux

How to use docker

Check the 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 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

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