vagrant-docker-exec

This plugin allows you to run docker exec commands from your host. When running docker in a proxy, this will save you the effort of sshing into the proxy to run docker exec. If you have multiple running containers, you can exec a command that runs on each container sequentially. Visit Docker's command reference for details on the exec command.

When running vagrant on Linux, interactive shells fail to return output with Vagrant 1.7.2 running on Ubuntu 14 Trusty Tahr. It appears to be a problem inherent to Vagrant 1.7.2 because built in commands like vagrant docker run also fail to return output from a shell. There is no known workaround at this time.

A container must be running before running docker exec, it will not be started automatically.

docker-exec requires Docker 1.3.0 or higher. On non-Linux system, the docker in boot2docker provided by Vagrant is version 1.2 and does not support the exec command, so a custom docker host is required.

You can find more information on setting up a custom docker host on the Vagrant blog but basically, create Vagrantfile.proxy and forward all your ports:

Vagrant.configure("2") do |config|
  config.vm.box = "phusion/ubuntu-14.04-amd64"
  config.vm.provision "docker"
  config.vm.network :forwarded_port, host: 8080, guest: 8080
  config.vm.provider :virtualbox do |vb|
    vb.name = "docker-proxy"
  end
end

And then use the vagrant_vagrantfile setting to reference your custom host in your Vagrantfile:

Vagrant.configure("2") do |config|
  config.vm.provider "docker" do |d|
    d.image   = "dockerfile/nginx"
    d.ports   = ["8080:80"]
    d.vagrant_vagrantfile = "./Vagrantfile.proxy"
  end
end

This plugin has been tested on Mac OS X and VirtualBox.

To install the plugin, run the following command:

vagrant plugin install vagrant-docker-exec

Periodically check for updates:

vagrant plugin update

A common use case for the exec command is to open a new shell in a running conatiner. To make it easy, run the docker-shell shortcut:

vagrant docker-shell [container]

In a single machine environment you can omit the container name and just run vagrant docker-shell.

docker-shell is a shortcut for docker-exec running Bash in an interactive shell:

vagrant docker-exec -t nginx -- bash

The syntax for docker-exec is:

vagrant docker-exec [options] [container] -- <command> [args]

Options are: -t, --[no-]tty Open an interactive shell --[no-]prefix Prefix output with machine names --[no-]detach Run in the background

When opening a shell in a multimachine environment, docker-exec -t (and docker-shell) must be followed by at least 1 container name defined by config.vm.define. For example, for this Vagrantfile

Vagrant.configure("2") do |config|
  config.vm.define "web" do |v|
    v.vm.provider "docker" do |d|
      d.image   = "dockerfile/nginx"
      d.ports   = ["8082:80"]
      d.name    = "nginx"
      d.vagrant_vagrantfile = "./Vagrantfile.proxy"
    end
  end
end

The vagrant identifier is web so the command to open a shell will be vagrant docker-exec -t web -- bash even though the command docker ps will list the container name as "nginx". To avoid confusion it's best to use the same name for config.vm.define and d.name.

Arguments after the double hyphen are sent to docker's exec command. For example, to create a new file in a container named nginx:

vagrant docker-exec web -- touch /var/www/html/test.html

If the command produces output, the output will be prefixed with the name of the container.

vagrant docker-exec nginx nginx2 -- ifconfig | grep inet
==> nginx:           inet addr:172.17.0.5  Bcast:0.0.0.0  Mask:255.255.0.0
==> nginx:           inet6 addr: fe80::42:acff:fe11:5/64 Scope:Link
==> nginx:           inet addr:127.0.0.1  Mask:255.0.0.0
==> nginx:           inet6 addr: ::1/128 Scope:Host
==> nginx2:           inet addr:172.17.0.4  Bcast:0.0.0.0  Mask:255.255.0.0
==> nginx2:           inet6 addr: fe80::42:acff:fe11:4/64 Scope:Link
==> nginx2:           inet addr:127.0.0.1  Mask:255.0.0.0
==> nginx2:           inet6 addr: ::1/128 Scope:Host

To omit the container name prefix, pass the option --no-prefix:

bundle exec vagrant docker-exec --no-prefix -- head -n 1 /etc/hosts

The name of the container is only required for interactive shells. To run a command on multiple running containers, omit the container name:

vagrant docker-exec -- hostname
==> nginx: 231e57e57825
==> nginx2: 6ebced94866b

You can also specify containers as you would any other vagrant command:

vagrant docker-exec /nginx\d?/ -- ps aux | grep www-data

Note that all exec commands run by docker are run as the root user.

William Kolean william.kolean@gmail.com