General FAQ

How do I configure my web container / vhosts so I can run multiple projects at once from the same web container?

You don’t. Seriously. This is a place where you must change your thinking from that of treating a server as a unit to treating the service as a unit. If you have multiple projects active at once, you’ll have a web serving container active for each of them. This is ok because containers are much lighter weight than full virtual machines, though you do want to be careful about starting too many at once. Consider that you will have a docker-compose file for each project you are working on, and each docker-compose file represents your application and all the services required to run it.
You could be running multiple docker-compose applications on a single Docker Host. Realistically, for the performance of your computer you would stop one docker-compose environment before you would run another.

How do I see what containers are running on my Docker Host?

If you want to see how many containers are present within your Docker Host VM and check on the status of them just run docker ps This will show you the containers running, the image they are based on, the ports they expose and the name of the container.

To see all the containers on the Docker Host both running and stopped use the command docker ps -a

Why do I have so many containers / cleanup?

Any time you finish a project or you need to reset things, you should clean up your containers for a project by running docker-compose rm. That will remove the instances for the containers specified in your docker compose file.

Additionally you can run devtools prune to clear out all stopped containers and any dangling images.

Is there any regular maintenance needed?

Yes, to keep your environment working smoothly and with current infrastructure configurations, implement a personal regimen of Routine Image Maintenance.

Working with multiple Docker versions [Homebrew]

If you have multiple versions installed, doing brew info docker-compose will list the versions you have installed. The one with the "*" will be the version that is active.

If you need to switch versions, use the brew switch command and run any additional commands like brew unlink .... (The switch command will provide next command steps if you need to link or unlink any formulae).


brew switch docker 1.9.1

Can I get .vm container names a Docker Host not created with DevTools?

Yes, with an important caveat that containers will not be able to resolve .vm addresses without reconfiguring the daemon.

The devtools dns command can accept a --name parameter to run the DNS services on an existing Docker Host

When we start a machine with devtools start, we do the following things:

  • Start a machine with the -dns= Docker daemon option set so that all containers will try dnsdock for DNS
  • Run dnsdock bound to to provide .vm addresses for all containers
  • Set up Mac OS X to route to the Docker virtual machine's IP so the host machine can access containers direct
  • Set up /etc/resolver/vm so that OS X will look up .vm addresses through DNS queries to

If you run devtools dns --name=$DOCKER_MACHINE_NAME, every step except the first will run, so your OS X host will be able to reach containers by their .vm addresses but other containers will not. This is the major difference between creating a machine with devtools start and applying the DNS configuration to an existing machine with devtools dns.

Monitoring of containers

If you need some insight into how many resources a given Docker container may be using, take advantage of the command docker stats <container name>. This handy command will show you CPU%, Memory%, Memory Usage vs Limit, and Network I/O.
It is rudimentary but can be very useful in the first line of inspection on a container.