docker

docker (compose) formatting

just display the name, service, state, and status of containers in a docker compose project:

docker compose ps --format 'table {{.Name}}\t{{.Service}}\t{{.State}}\t{{.Status}}'

and for docker ps:

docker ps --format 'table {{.ID}}\t{{.Names}}\t{{.RunningFor}}\t{{.Status}}\t{{.Ports}}'

exec as other user (e.G. root)

with docker exec (where ac0 is the container id):

docker exec -it -u root ac0 sh

or with docker compose (znc is the container name):

docker compose exec -u root znc sh

docker logs

the default json log can become pretty large if you’re running a container for weeks. there are multiple options for logging, to simply use syslog globally for all containers:

create or edit /etc/docker/daemon.json:

{
  "log-driver": "syslog"
}

or like this:

{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "10m",
    "max-file": "3"
  }
}

changes in the daemon.json only apply to new containers, not existing.

docker cleanup

get rid of exited containers:

docker rm $(docker ps -aq -f status=exited)

get rid of unused images:

docker rmi $(docker images -a|grep none|awk {'print $3'})

docker (compose) resource monitoring

quickly get resource usage, such as cpu and memory, for each container in a docker compose project:

docker stats --no-stream $(docker compose ps -q)

get the total usage of the whole project combined:

docker stats --no-stream --format "table {{.CPUPerc}}\t{{.MemUsage}}" $(docker compose ps -q) | awk 'NR>1 {cpu+=$1; mem+=$2} END {print "Total CPU: " cpu "%, Total Memory: " mem}'

backup / export docker volumes

backup a single docker volume

backup the volume named foobar:

docker run --rm -v "foobar:/data" -v "$(pwd):/backup" alpine tar czf /backup/foobar_$(date +%F).tar.gz -C /data .

restore:

docker run --rm -v "foobar:/data" -v "$(pwd):/backup" alpine tar xzf /backup/foobar_2025-10-25.tar.gz -C /data

backup all docker volumes

docker volume ls -q | xargs -I {} docker run --rm -v "{}:/data" -v "$(pwd):/backup" alpine tar czf /backup/{}_$(date +%F).tar.gz -C /data .

backup docker volumes using a filter

of all volumes starting with the name foo, useful for docker compose projects:

docker volume ls -q -f name=^foo | xargs -I {} docker run --rm -v "{}:/data" -v "$(pwd):/backup" alpine tar czf /backup/{}_$(date +%F).tar.gz -C /data .

docker and ipv6

enable ipv6 with docker compose

create a new network to your compose.yaml and add this network to your container(s), example:

services:
  pihole:
    image: pihole/pihole:latest
    networks:
      - leela-network
    ports:
      - 53:53/tcp
      - 53:53/udp
    environment:
      TZ: Europe/Paris
    volumes:
      - pihole-etc:/etc/pihole
      - pihole-dnsmasq:/etc/dnsmasq.d
    restart: unless-stopped

networks:
  leela-network:
    enable_ipv6: true

the above enables ipv6 and ipv4 for your container

more docker ipv6 stuff

this is for your /etc/docker/daemon.json file. it might not exist.

{
  "log-driver": "journald",
  "ipv6": true,
  "fixed-cidr-v6": "fd00:dead:beef:c0::/80",
  "experimental": true,
  "ip6tables": true
}

dns dpkg