Docker

see also: Docker Compose / Docker Swarm

• ctop – top like tool for container metrics.

Start interactive shell in container

docker exec -ti container sh

List stopped containers

docker ps --filter "status=exited"

Get command used to start a Docker container

docker inspect -f '{{json .Config}}' CONTAINERID | jq '.Env'

Get IP of a container

docker inspect --format '{{ .NetworkSettings.IPAddress }}' CONTAINERID

docker system prune -a
 
WARNING! This will remove:
    - all stopped containers
    - all volumes not used by at least one container
    - all images without at least one container associated to them
Are you sure you want to continue? [y/N] y

du -t 100M -shc /var/lib/docker/overlay2/*/diff | sort

(source)

Further reading:

• Docker garbage collector cronjob
• https://stackoverflow.com/questions/46672001/is-it-safe-to-clean-docker-overlay2
• https://docs.docker.com/config/pruning/

# delete all volumes not in use or dangling
docker volume rm $(docker volume ls -qf dangling=true)
 
# same
docker system prune --all --volumes --force

docker inspect -f '{{ range .Mounts }}{{ .Source }}:{{ .Destination }} {{ end }}' $(docker-compose ps -q)

• Bivac - backup container volumes using Restic

# Backup
docker exec CONTAINER /usr/bin/mysqldump -u root --password=root DATABASE > backup.sql
 
# Restore
cat backup.sql | docker exec -i CONTAINER /usr/bin/mysql -u root --password=root DATABASE

• Which Host OS is best?

see also: The New Minimalist Operating Systems (blog.docker.com)

• Rancher
• Project Atomic
• CoreOS
• Snappy Ubuntu Core

to be able to access mounts with enabled SELinux, you need to specify :z or :Z to the bind mount option.

See also: https://docs.docker.com/storage/bind-mounts/#configure-the-selinux-label

docker exec CONTAINERNAME mysql_upgrade "-uroot" "-pROOTPASSWORD"

• Tiny Docker Pieces, Loosely Joined (data-only Docker containers)
• Understanding how uid and gid work in Docker containers

• http://jonaskunze.com/restrict-user-to-its-own-container-using-docker/
• https://github.com/rootless-containers/runrootless
• https://www.jujens.eu/posts/en/2018/Feb/25/multiple-docker/