How to use docker-machine on a private server?

Question

I want to install docker hosts on a server running CentOS7(that's running in Virtualbox on my PC if it matters).

I'm aware that there are drivers for multiple cloud providers (Amazon, Google, DigitalOcean etc) but I can't figure out what to do if I want to use my own private server.

I've tried using --driver generic with the guest OS's IP, and an SSH key I created and copied using ssh-keygen and ssh-copy-id but I got

$ docker-machine create -d generic --generic-ip-address=<IP> --generic-ssh-key ~/.ss
h/id_rsa --generic-ssh-user <user> centos

Running pre-create checks...
Creating machine...
(centos) Importing SSH key...
Waiting for machine to be running, this may take a few minutes...
Detecting operating system of created instance...
Waiting for SSH to be available...
Detecting the provisioner...
Provisioning with centos...
Error creating machine: Error running provisioning: exit status 1

What am I doing wrong?

Can it have something to do with the fact that I installed CentOS in Virtualbox?

Answer 1

Yes you can use docker-machine to provision and control docker-engine on a linux server, i.e. import an existing linux server as a Docker Machine. There are several requirements for this:

1. Only a few OS are supported, see https://docs.docker.com/machine/drivers/os-base/. Support for CentOS is experimental at the moment
2. Your SSH key need to be either without password, or managed by ssh-agent.
3. Your user account on the server need to be able to run sudo without password (see this link https://stackoverflow.com/a/24648413/4190526 on how to do it)

Once the requirements are satisfied, you can import your server as a Docker Machine using one of the methods below

1. If your SSH key has no password

   docker-machine create -d generic --generic-ip-address server-ip --generic-ssh-key key-file --generic-ssh-user username machine-name
   

2. If you use ssh-agent to manage your key

   docker-machine create -d generic --generic-ip-address server-ip --generic-ssh-user username machine-name
   

Then you'll be able to use docker-machine commands on your local machine to control this remote server. This means that you can start, stop, kill, restart the server, so use it with extreme caution

Also, in general, due to the requirements listed at the beginning, and the fact that you'll be able to stop or kill the server, I would NOT recommend doing this. It is much safer to SSH into your server and do everything from there.