How to check on Linux if Docker is running

Docker is a popular tool for developing and running applications in containers. It can be used on a variety of platforms, including Linux.

There are a few ways to check if Docker is running on Linux.

1. Use the systemctl command.

sudo systemctl status docker

If the Docker daemon is running, you will see an output similar to this:

● docker.service - Docker Application Container Engine
 Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
 Active: active (running) since Wed 2023-08-03 14:27:03 UTC; 3h 3min ago
 Main PID: 1326 (dockerd)
  Tasks: 27
 Memory: 15.4M
  CPU: 8ms
 CGroup: /system.slice/docker.service
   └─1326 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock

1. Use the docker info command.

docker info

If the Docker daemon is running, you will see an output similar to this:

Client:
 Version:           20.10.8
 ...

Server:
 Version:           20.10.8
 ...

1. Check the process ID of the Docker daemon.

   The Docker daemon writes its process ID to the file /var/run/docker.pid. You can check if the Docker daemon is running by checking if this file exists and if the process ID associated with it is running.

sudo cat /var/run/docker.pid

If the Docker daemon is running, you will see a number. If the number is not running, the Docker daemon is not running.