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

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 question was ambiguous, with some people interpreting it as "check docker engine", and others as "check docker container"]

This question is related to bash docker

The answer is


container status: true/false

# docker inspect --format '{{json .State.Running}}' container-name
true
#

For the answer to your first question refer to this answer - https://stackoverflow.com/a/65447848/4691279

For your second question - you can use command like docker ps --filter "name=<<<YOUR_CONTAINER_NAME>>>" to check whether a particular container is running or not.

  • If Docker and Container both are running then you will get output like below:

    $ docker ps --filter "name=nostalgic_stallman"
    
    CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES       
    9b6247364a03        busybox             "top"               2 minutes ago       Up 2 minutes                            nostalgic_stallman
    
  • If Docker is not running then you will get an error message saying docker daemon is not running.

  • If Docker running but Container is not running then you will not get the container name in the output of this command.


docker ps -a

You can see all docker containers whether it is alive or dead.


you can check docker state using: systemctl is-active docker

?  ~  systemctl is-active docker
active

you can use it as:

?  ~  if [ "$(systemctl is-active docker)" = "active" ]; then echo "is alive :)" ; fi
is alive :)

?  ~  sudo systemctl stop docker

?  ~  if [ "$(systemctl is-active docker)" = "active" ]; then echo "is alive :)" ; fi
 * empty response *

Run:

docker version

If docker is running you will see:

Client: Docker Engine - Community
 Version:           ...
 [omitted]

Server: Docker Engine - Community
 Engine:
  Version:          ...
 [omitted]

If docker is not running you will see:

Client: Docker Engine - Community
 Version:           ...
 [omitted]

Error response from daemon: Bad response from Docker engine

I have a more fleshed out example of using some of the work above in the context of a Gitea container, but it could easily be converted to another container based on the name. Also, you could probably use the docker ps --filter capability to set $GITEA_CONTAINER in a newer system or one without docker-compose in use.

# Set to name or ID of the container to be watched.
GITEA_CONTAINER=$(./bin/docker-compose ps |grep git|cut -f1 -d' ')

# Set timeout to the number of seconds you are willing to wait.
timeout=500; counter=0
# This first echo is important for keeping the output clean and not overwriting the previous line of output.
echo "Waiting for $GITEA_CONTAINER to be ready (${counter}/${timeout})"
#This says that until docker inspect reports the container is in a running state, keep looping.
until [[ $(docker inspect --format '{{json .State.Running}}' $GITEA_CONTAINER) == true ]]; do

  # If we've reached the timeout period, report that and exit to prevent running an infinite loop.
  if [[ $timeout -lt $counter ]]; then
    echo "ERROR: Timed out waiting for $GITEA_CONTAINER to come up."
    exit 1
  fi

  # Every 5 seconds update the status
  if (( $counter % 5 == 0 )); then
    echo -e "\e[1A\e[KWaiting for $GITEA_CONTAINER to be ready (${counter}/${timeout})"
  fi

  # Wait a second and increment the counter
  sleep 1s
  ((counter++))

done

You can also check if a particular docker container is running or not using following command:

docker inspect postgres | grep "Running"

This command will check if for example my postgres container is running or not and will return output as "Running": true

Hope this helps.


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.


Any docker command (except docker -v), like docker ps If Docker is running, you'll get some valid response, otherwise you'll get a message that includes "Is your docker daemon up and running?"

You can also check your task manager.


Run this command in the terminal:

docker ps

If docker is not running, you wil get this message:

Error response from daemon: dial unix docker.raw.sock: connect: connection refused


List all containers:

docker container ls -a

ls = list
-a = all

Check the column "status"


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.


For OS X users (Mojave 10.14.3)

Here is what i use in my Bash script to test if Docker is running or not

# Check if docker is running
if ! docker info >/dev/null 2>&1; then
    echo "Docker does not seem to be running, run it first and retry"
    exit 1
fi

I ended up using

docker info

to check with a bash script if docker engine is running.


How I check in SSH.Run:

systemctl

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

Its a docker or WSL container.


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.


on a Mac you might see the image:

enter image description here

if you right click on the docker icon then you see:

enter image description here

alternatively:

docker ps

and

docker run hello-world


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>