docker-machine ssh

Estimated reading time: 3 minutes

Log into or run a command on a machine using SSH.

To login, just run docker-machine ssh machinename:

$ docker-machine ssh dev

                        ##        .
                  ## ## ##       ==
               ## ## ## ##      ===
           /""""""""""""""""\___/ ===
      ~~~ {~~ ~~~~ ~~~ ~~~~ ~~ ~ /  ===- ~~~
           \______ o          __/
             \    \        __/
              \____\______/
 _                 _   ____     _            _
| |__   ___   ___ | |_|___ \ __| | ___   ___| | _____ _ __
| '_ \ / _ \ / _ \| __| __) / _` |/ _ \ / __| |/ / _ \ '__|
| |_) | (_) | (_) | |_ / __/ (_| | (_) | (__|   <  __/ |
|_.__/ \___/ \___/ \__|_____\__,_|\___/ \___|_|\_\___|_|
Boot2Docker version 1.4.0, build master : 69cf398 - Fri Dec 12 01:39:42 UTC 2014
docker@boot2docker:~$ ls /
Users/   dev/     home/    lib/     mnt/     proc/    run/     sys/     usr/
bin/     etc/     init     linuxrc  opt/     root/    sbin/    tmp      var/

You can also specify commands to run remotely by appending them directly to the docker-machine ssh command, much like the regular ssh program works:

$ docker-machine ssh dev free

total         used         free       shared      buffers
Mem:       1023556       183136       840420            0        30920
-/+ buffers:             152216       871340
Swap:      1212036            0      1212036

Commands with flags work as well:

$ docker-machine ssh dev df -h

Filesystem                Size      Used Available Use% Mounted on
rootfs                  899.6M     85.9M    813.7M  10% /
tmpfs                   899.6M     85.9M    813.7M  10% /
tmpfs                   499.8M         0    499.8M   0% /dev/shm
/dev/sda1                18.2G     58.2M     17.2G   0% /mnt/sda1
cgroup                  499.8M         0    499.8M   0% /sys/fs/cgroup
/dev/sda1                18.2G     58.2M     17.2G   0%
/mnt/sda1/var/lib/docker/aufs

If you are using the “external” SSH type as detailed in the next section, you can include additional arguments to pass through to the ssh binary in the generated command (unless they conflict with any of the default arguments for the command generated by Docker Machine). For instance, the following command forwards port 8080 from the default machine to localhost on your host computer:

$ docker-machine ssh default -L 8080:localhost:8080

Different types of SSH

When Docker Machine is invoked, it checks to see if you have the venerable ssh binary around locally and attempts to use that for the SSH commands it needs to run, whether they are a part of an operation such as creation or have been requested by the user directly. If it does not find an external ssh binary locally, it defaults to using a native Go implementation from crypto/ssh. This is useful in situations where you may not have access to traditional UNIX tools, such as if you are using Docker Machine on Windows without having msysgit installed alongside of it.

In most situations, you do not need to worry about this implementation detail and Docker Machine acts sensibly out of the box. However, if you deliberately want to use the Go native version, you can do so with a global command line flag / environment variable like so:

$ docker-machine --native-ssh ssh dev

There are some variations in behavior between the two methods, so report any issues or inconsistencies if you come across them.

machine, ssh, subcommand