Troubleshooting

Information about how to troubleshoot docker containers.

Troubleshooting Docker Containers

1. Get the IP address. To do this, run the following command.

    docker inspect $(dl) | grep -wm1 IPAddress | cut -d '"' -f 4

   Or, install jQuery and run the following command.

   docker inspect $(dl) | jq -r '.[0].NetworkSettings.IPAddress'

   Or install go template and run the following command.

   docker inspect -f '{{ .NetworkSettings.IPAddress }}' <container_name>

   To pass a build argument when building an image from Dockerfile:

   DOCKER_HOST_IP=`ifconfig | grep -E "([0-9]{1,3}\.){3}[0-9]{1,3}" | grep -v 127.0.0.1 | awk '{ print $2 }' | cut -f2 -d: | head -n1`
   echo DOCKER_HOST_IP = $DOCKER_HOST_IP
   docker build \
     --build-arg ARTIFACTORY_ADDRESS=$DOCKER_HOST_IP 
     -t sometag \
     some-directory/

2. Get port mapping

   docker inspect -f '{{range $p, $conf := .NetworkSettings.Ports}} {{$p}} -> {{(index $conf 0).HostPort}} {{end}}' <containername>

3. Find containers by regular expression

   for i in $(docker ps -a | grep "REGEXP_PATTERN" | cut -f1 -d" "); do echo $i; done

4. Get environment settings.

   docker run --rm ubuntu env

5. Kill running containers.

   docker kill $(docker ps -q)

6. Delete all containers (force!! running or stopped containers).

   docker rm -f $(docker ps -qa)

7. Delete old containers.

   docker ps -a | grep 'weeks ago' | awk '{print $1}' | xargs docker rm

8. Delete stopped containers.

   docker rm -v $(docker ps -a -q -f status=exited)

9. Delete containers after stopping.

   docker stop $(docker ps -aq) && docker rm -v $(docker ps -aq)

10. Delete dangling images.

    docker rmi $(docker images -q -f dangling=true)

11. Delete all images.

    docker rmi $(docker images -q)

12. Delete dangling volumes. As of Docker 1.9.0:

    docker volume rm $(docker volume ls -q -f dangling=true)

    In 1.9.0, the filter dangling=false does not work. It is ignored and lists all volumes.
13. Show image dependencies.

    docker images -viz | dot -Tpng -o docker.png

14. Slimming down Docker containers. Cleaning APT in a RUN layer: This must be done in the same layer as that of the other APT commands. If not, the previous layers will still contain the original information and your images will still be large.

    RUN {apt commands} \

     && apt-get clean \

     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*

    Flatten an image:

    ID=$(docker run -d image-name /bin/bash)

    docker export $ID | docker import – flat-image-name

    For backup:

    ID=$(docker run -d image-name /bin/bash)

    (docker export $ID | gzip -c > image.tgz)

    gzip -dc image.tgz | docker import - flat-image-name

Information on Running Docker Containers

• docker ps displays running containers.
• docker logs gets logs from the container. (You can use a custom log driver, but logs are available only for json-file and journald in 1.10).
• docker inspect inspects all the information of a container (including the IP address).
• docker events gets events from the container.
• docker port displays the public facing port of the container.
• docker top displays the running processes in container.
• docker stats displays the containers' resource usage statistics.
• docker diff displays the changed files in the container's FS.
• docker ps -a displays running and stopped containers.
• docker stats --all displays a running list of containers.
• docker update updates a container's resource limits.

To check the CPU, memory, and network I/O usage of a single container:

docker stats <container>

For all containers listed by ID:

docker stats $(docker ps -q)

For all containers listed by name:

docker stats $(docker ps --format '{{.Names}}')

For all containers listed by image:

docker ps -a -f ancestor=ubuntu

To remove all untagged images:

docker rmi $(docker images | grep “^” | awk '{split($0,a," "); print a[3]}')

To remove container by a regular expression:

docker ps -a | grep wildfly | awk '{print $1}' | xargs docker rm -f

To remove all exited containers:

docker rm -f $(docker ps -a | grep Exit | awk '{ print $1 }')