Docker has added a new feature to allow alternate logging drivers, and soon you’ll be able to use
journald as a supported driver.
With Docker 1.6 they support json-file, which is the old default, syslog, or no logging at all.
If you ran your docker daemon with the
--log-driver=syslog option, any output from a container would go directly to system syslog daemon, and usually end up in /var/log/messages.
I added a patch to support journald as a logging driver, and it was recently merged.
In docker-1.7 you will have the option to use
--log-driver=journald on either your docker daemon to cause all of your container logging to go directly to the journal, or you could use the –log-driver=journald on a docker run/create line, so you could get individual containers running with different logging drivers.
To test this I set up my docker daemon to run with the following options.
docker -d --selinux-enabled --log-driver=journald
Now I run a simple container.
docker run fedora echo "Dan Walsh was here"
Then I look up the container ID for the newly created container, and I can use journalctl to examine the content.
journalctl MESSAGE_ID=cdf02c627e27 -- Logs begin at Mon 2015-04-06 16:06:42 EDT, end at Fri 2015-04-24 08:40:38 EDT. -- Apr 20 15:06:39 dhcp-10-19-62-196.boston.devel.redhat.com docker: Dan Walsh was here
docker logs command only works with the json-file backend. But I hope to eventually get the docker daemon to communicate with the journald to get this information. Of course if anyone wants to take a stab at this, we would welcome your effort.
As mentioned, the journald backend for
--log-driver is not shipping in Docker today, but should be available in the 1.7 release. Keep reading here or follow @projectatomic for updates on new and interesting features in Docker.