Docker sysadmin

Post by **Mihai** » 2024 Feb 19, 11:37

This list will be upgraded with time.

Update all images:

docker images | grep -v REPOSITORY | awk '{print $1}' | xargs -L1 docker pull

Remove all images with no tags ( <none> ):

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docker image ls | egrep none | awk '{print $3}' | xargs docker image rm

Show disk usage detailed

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docker system df -v

Show IP address for every container ( docker-compose only )

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docker inspect -f '{{.Name}} - {{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}}' $(docker ps -aq)

Show IP address for every container

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docker inspect -f '{{range .NetworkSettings.Networks}}{{.IPAddress}}{{end}} %tab% {{.Name}}' $(docker ps -aq ) | sed 's#%tab%#\t#g' | sed 's#/##g' | sort -t . -k 1,1n -k 2,2n -k 3,3n -k 4,4n

Create bridge network

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docker network create --driver=bridge --subnet=172.28.0.0/16 --ip-range=172.28.5.0/24 --gateway=172.28.5.254 br0

Create MacVLAN network with ip-range

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docker network create -d macvlan --subnet=192.168.0.0/24 --gateway=192.168.0.1  --ip-range=192.168.0.64/26 -o parent=eth0 public_network_mac_vlan

IP Range will be:

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HostMin:   	192.168.0.65          		11000000.10101000.00000000.01 000001
HostMax:   	192.168.0.126         		11000000.10101000.00000000.01 111110

Create and activate heathcheck user mariadb

Create filename .my-healthcheck.cnf in the root directory of the docker application and add the following content inside:

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[mariadb-client]
port=3306
socket=/run/mysqld/mysqld.sock
user=healthcheck
password=addYouRPas55W0rDH3R3
protocol=tcp

Link filename in volumes for your application:

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/apps/docker/docker-containers/application-name/.my-healthcheck.cnf:/var/lib/mysql/.my-healthcheck.cnf

Add username healthcheck in your database and grant minimal privileges:

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CREATE USER 'healthcheck'@'localhost' IDENTIFIED BY 'addYouRPas55W0rDH3R3';
CREATE USER 'healthcheck'@'127.0.0.1' IDENTIFIED BY 'addYouRPas55W0rDH3R3';
GRANT USAGE ON *.* TO 'healthcheck'@'localhost';
GRANT USAGE ON *.* TO 'healthcheck'@'127.0.0.1';

Add configuration to docker-compose.yml under the DB app:

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    healthcheck:
      test: ["CMD", "healthcheck.sh", "--connect", "--innodb_initialized"]
      start_period: 10s
      interval: 10s
      timeout: 5s
      retries: 3

Result will be similar to the following:

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CONTAINER ID    IMAGE                 COMMAND                      CREATED           STATUS                            PORTS        NAMES
38d083416ca8    mariadb:latest        docker-entrypoint.s…"        8 minutes ago     Up 8 minutes (healthy)            3306/tcp     mariadb_test_app

Pull ALL images with lowercase fallback

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docker images --format '{{.Repository}}:{{.Tag}}' \
  | grep -v '<none>' \
  | while read -r IMG; do
        # Skip empty or malformed entries
        [[ -z "$IMG" ]] && continue
        [[ "$IMG" != *:* ]] && continue
        # Extract repo + tag
        REPO="${IMG%%:*}"
        TAG="${IMG##*:}"
        # Skip empty
        [[ -z "$REPO" || -z "$TAG" ]] && continue
        # Convert to lowercase safely
        REPO_LOWER=$(echo "$REPO" | tr '[:upper:]' '[:lower:]')
        TAG_LOWER=$(echo "$TAG" | tr '[:upper:]' '[:lower:]')
        FINAL="${REPO_LOWER}:${TAG_LOWER}"
        echo "→ Pulling $FINAL ..."
        docker pull "$FINAL"
    done

Restrict Log and Enable IPv6

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vim /etc/docker/daemon.json

Add the following configuration:

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{
  "log-driver": "json-file",
  "log-opts": {
    "max-size": "5g",
    "max-file": "3"
  },
  "ipv6": true,
  "fixed-cidr-v6": "fd00::/80",
  "ip6tables": true
}

Create container with passthrough network configuration to the network router

This is the only way to make containers act like physical devices on your LAN. They will bypass the Docker bridge and communicate directly with your router. This will create the dual-stack-net.

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services:
  my-app:
    image: nginx:latest
    networks:
      dual-stack-net:
        # Optional: Assign static IPs if your network requires them
        ipv4_address: 192.168.1.50
        ipv6_address: 2a02:2f05:204:3701::50

networks:
  dual-stack-net:
    name: lan_ipv6
    driver: macvlan
    enable_ipv6: true
    driver_opts:
      parent: eth0
    ipam:
      config:
        # IPv4 Configuration
        - subnet: 192.168.1.0/24
          gateway: 192.168.1.1
        # IPv6 Configuration
        - subnet: 2a02:2f15:2204:3701::/64
          gateway: 2a02:2f15:2204:3701:c29f:e1ff:fe1d:ddab