CODEWITHSUNDEEP
dockercentos7systemd
David M. Karr
David M. Karr

Reputation: 15235

docker run from systemd service starts but exits immediately, and restarts, but docker run from shell works fine

On my CentOS 7.2 box, with Docker 1.10.3, I successfully tested the following (running as root):

docker run --name usljavadoc_server -p 80:80 -p 443:443 -v /opt/app/uslJavadoc/:/var/www/html/ -d eboraas/apache

Content automatically deployed to "/opt/app/uslJavadoc" was servable from the apache running in the container.

So, my next step was getting this to work with systemd, so I created "/etc/systemd/system/docker-usljavadoc.service" with the following contents:

[Unit]
Description=Apache serving USL Javadoc
Requires=docker.service
After=docker.service

[Service]
TimeoutStartSec=0
Restart=always
ExecStart=/usr/bin/docker run --name usljavadoc_server -p 80:80 -p 443:443 -v /opt/app/uslJavadoc/:/var/www/html/ -d eboraas/apache
ExecStop=/usr/bin/docker stop -t 2 usljavadoc_server
ExecStopPost=/usr/bin/docker rm -f usljavadoc_server

[Install]
WantedBy=default.target

I manually reloaded systemd and started the service. I verified that the browser on another box could reach the apache process and get the properly served content. I then rebooted to make sure it works on reboot. Still worked.

So, I thought I was done. However, what I noticed when I looked closer is that the service successfully starts, but it exits immediately after starting, and then restarts. This is happening continuously. As it's just plain html content being served (a javadoc tree), and that the service immediately restarts, users might not even notice there is a problem, but it definitely shouldn't be doing this.

Any ideas why this "docker run" works fine from the shell, and seems to start fine from systemd, but exits immediately after a couple of seconds?

Upvotes: 2

Views: 2122

Answers (1)

lvthillo
lvthillo

Reputation: 30841

Remove the -d option from your run command.

ExecStart=/usr/bin/docker run --name usljavadoc_server -p 80:80 -p 443:443 -v /opt/app/uslJavadoc/:/var/www/html/ eboraas/apache

In the docker docs is described:

To start a container in detached mode, you use -d=true or just -d option. By design, containers started in detached mode exit when the root process used to run the container exits.

After the ExecStart your client exits. Systemd will see this as an error and execute your ExecStop commands + try to restart (restart=always)

Upvotes: 6

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