How to check if the docker engine and a docker container are running?

Question

In a script, I need to check:

a) Is the docker engine running?
b) Given a container name, is that docker container running?

[the initial wording of this

Answer 1

Sometimes you don't know the full container name, in this case this is what worked for me:

if docker ps | grep -q keyword
then 
    echo "Running!"
else
    echo "Not running!"
    exit 1
fi

We list all the running container processes (docker ps -a would show us also not running ones, but that's not what I needed), we search for a specific word (grep part) and simply fail if we did not find at least one running container whose name contains our keyword.

Answer 2

You can check with this command systemctl status docker it will show the status of the docker. If you want to start you can use systemctl start docker instead of systemctl you can try also with service, service docker status and service docker start respectively.

Answer 3

If the underlying goal is "How can I start a container when Docker starts?"

We can use Docker's restart policy

To add a restart policy to an existing container:

Docker: Add a restart policy to a container that was already created

Example:

docker update --restart=always <container>

Answer 4

If you are looking for a specific container, you can run:

if [ "$( docker container inspect -f '{{.State.Running}}' $container_name )" == "true" ]; then ...

To avoid issues with a container that is in a crash loop and constantly restarting from showing that it's up, the above can be improved by checking the Status field:

if [ "$( docker container inspect -f '{{.State.Status}}' $container_name )" == "running" ]; then ...

If you want to know if dockerd is running itself on the local machine and you have systemd installed, you can run:

systemctl show --property ActiveState docker

You can also connect to docker with docker info or docker version and they will error out if the daemon is unavailable.

Answer 5

How I check in SSH.Run:

systemctl

If response: Failed to get D-Bus connection: Operation not permitted

Its a docker or WSL container.