Difference between revisions of "Docker"

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=== Grub ===
=== 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
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>, then upgrade your grub
<pre>GRUB_CMDLINE_LINUX_DEFAULT="... e=memory swapaccount=1"</pre>
<pre>GRUB_CMDLINE_LINUX_DEFAULT="... e=memory swapaccount=1"</pre>
=== Extlinux ===
=== Extlinux ===

Revision as of 18:27, 18 February 2020

Alpine makes a great docker container, because it is so small and optimized to be run in RAM. It 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.


Run apk add docker 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:


then run apk update to index the repository.

To start the Docker daemon at boot, run:

rc-update add docker boot

Then to start the Docker daemon manually, run:

service docker start

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:

sysctl -w kernel.grsecurity.chroot_deny_chmod=0

sysctl -w kernel.grsecurity.chroot_deny_mknod=0

For more information, have a look at the 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:

apk add py-pip

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

apk add python-dev libffi-dev openssl-dev gcc libc-dev make

Then install docker-compose, run:

pip install docker-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

and add in /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 will find all possible configurations here[1].

Example: How to install docker from Arch


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

You may, probably, encounter this message by executing docker info. To correct this situation we have to enable the cgroup_enable=memory swapaccount=1

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

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;


Well; if you use Grub it is like any other linux and you just have to add the cgroup condition into /etc/default/grub, then upgrade your grub

GRUB_CMDLINE_LINUX_DEFAULT="... e=memory swapaccount=1"


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

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

than update the config and reboot


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.


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