The daemon will refuse to restart when a PID file is present. This can be more reliable than looking for docker.pid – if the daemon crashes, docker.pid could get left behind after the process is gone. There’s an active Docker daemon on your machine if top matches a dockerd process. This accepts a process name and returns the first matching ID: pidof dockerd You can also get the process ID with the pidofcommand. Reading the file gives you the ID which you can use with tools like top to get more information about the Docker process: cat /var/run/docker.pid
You can use this technique to create programmatic scripts that check whether the daemon’s alive. When this file exists, Docker should be running and ready for CLI connections. The daemon writes its process ID to /var/run/docker.pid each time it starts up. Inspecting Process DetailsĪnother way to check for a running Docker daemon is by inspecting its process ID file. Rebooting your host machine or restarting the Docker service with systemctl restart docker can help alleviate transient issues too. When there’s no obvious resolution available, manually start the daemon in debugging mode to get more information on its startup routine. You should review the service’s startup logs shown later in the systemctl command output as these usually contain hints that let you work out what went wrong. If you see a status of failed in red, the daemon couldn’t start due to an error. The status should change to active (running) after the daemon starts. Try to bring it up by running sudo systemctl start docker. sudo systemctl status dockerĬheck what’s displayed under “Active.” If you see active (running) in green, the Docker daemon is running and your containers should be up.Īn active state of inactive indicates the service has stopped. This covers the majority of popular operating systems including Debian, Ubuntu, CentOS, and Red Hat. You can check Docker’s status with systemctl on distributions that use Systemd for service management. When the daemon’s not running, you’ll see a “can’t connect to Docker daemon” message each time you use the docker CLI.
#DOCKER DAEMON LOGS CENTOS HOW TO#
Here’s how to check whether Docker’s daemon is up so you can diagnose issues with containers and the docker command.
#DOCKER DAEMON LOGS CENTOS OFFLINE#
CLI commands won’t work and your containers will usually go offline if the daemon stops. Docker uses a daemon-based architecture where the CLI connects to a long-lived process running separately on your machine or a remote host.