Docker: Difference between revisions
WhyNotHugo (talk | contribs) (→Installation: explanation on rootless docker) |
(On a SBC board like a Raspberry Pi that lacks a battery to retain system time it's important for NTP to start and determine the current time before Docker starts. Otherwise a node in a swarm will reject CAs because they're from the future.) |
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To start the Docker daemon at boot, see [[Alpine_Linux_Init_System]]. | To start the Docker daemon at boot, see [[Alpine_Linux_Init_System]]. | ||
rc-update add docker | rc-update add docker default | ||
service docker start | service docker start | ||
Revision as of 04:29, 10 February 2023
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 username docker
To start the Docker daemon at boot, see Alpine_Linux_Init_System.
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 requires the docker-rootless-extras
package and enabling the cgroups
service:
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-compose' is in the 'Community' repository starting with Alpine Linux 3.10.
apk add 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
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[1].
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 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; } 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
The best documentation on using Docker and creating containers is at the official docker site. Adding anything to it here would be redundant.
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.