Docker: Difference between revisions

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.

@@ Line 1: / Line 1: @@
 == Installation ==
-The Docker package is in the 'Community' repository. See [[Alpine_Linux_package_management]] how to add a repository.
+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 `docker` group.
+Connecting to the Docker daemon through its socket requires you to add yourself to the <code>docker</code> group.
-  addgroup username docker
+  addgroup ${USER} docker
-To start the Docker daemon at boot, see [[Alpine_Linux_Init_System]].
+To start the Docker daemon at boot, see [[OpenRC]].
-  rc-update add docker boot
+  rc-update add docker default
   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:}}
+=== Docker rootless ===
- sysctl -w kernel.grsecurity.chroot_deny_chmod=0
+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.
- 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 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:
-This weakening of security is not necessary to do with Alpine 3.4.x and Docker 1.12 as of August 2016.
+ 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 ===
-'docker-compose' is in the 'Community' repository starting with Alpine Linux 3.10.
+{{Pkg|docker-cli-compose}} is in the ''community'' repository starting with Alpine Linux 3.15.
-  apk add docker-compose
+  apk add docker-cli-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 ==
@@ Line 44: / Line 39: @@
 </pre>
-add to '''/etc/docker/daemon.json'''
+add to <code>/etc/docker/daemon.json</code>
 <pre>
@@ Line 52: / Line 47: @@
 </pre>
-''You may also consider these options : '''
+''You may also consider these options : ''
          "experimental": false,
          "live-restore": true,
@@ Line 59: / Line 54: @@
          "no-new-privileges": false'''''
-You'll find all possible configurations here[https://docs.docker.com/engine/reference/commandline/dockerd/#daemon-configuration-file].
+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 ==
@@ Line 71: / Line 66: @@
 ==== Alpine 3.8 ====
-It may not have been the case before, but with Alpine 3.8, you must config cgroups properly
+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.
+{{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>
@@ Line 105: / Line 100: @@
 <code>update-extlinux</code>
-== '''How to use docker''' ==
+== 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/'''
+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 user images and learn from the syntax in contributed 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 on the website by a blue ribbon.
+Official Docker image files are denoted on the website by a special badge.
 == See also ==