Docker Machine is a tool that makes it easy to provision and manage multiple Docker hosts remotely from your personal computer. Such servers are commonly referred to as Dockerized hosts, and as a matter of course, can be used to run Docker containers.
While Docker Machine can be installed on a local or a remote system, the most common approach is to install it on your local computer (native installation or virtual machine) and use it to provision Dockerized remote servers.
Though Docker Machine can be installed on most Linux distribution as well as Mac OS X and Windows, in this tutorial, we’ll be installing it on your local machine running Ubuntu 16.04 and use it to provision Dockerized DigitalOcean Droplets.
To follow this tutorial, you will need the following:
In this step, we’ll work through the process of installing Docker Machine on your local computer running Ubuntu 16.04.
To download and install the Docker Machine binary, type:
The name of the file should be docker-machine-Linux-x86_64
. Rename it to docker-machine
to make it easier to work with:
Make it executable:
Move or copy it to the usr/local/bin
directory so that it will be available as a system command.
Check the version, which will indicate that it’s properly installed:
The output should be similar to
Outputdocker-machine version 0.14.0, build 89b8332
There are three bash scripts in the Docker Machine GitHub repository designed to facilitate the usage of the docker
and docker-machine
commands. They provide command completion and bash-prompt customization.
In this step, we’ll install these three scripts on your local machine. They will be downloaded and installed into the /etc/bash_completion.d
directory.
The first script allows you to see the active machine from your bash prompt. This comes in handy when you are working with and switching between multiple Dockerized machines. The script is called docker-machine-prompt.bash
. To download it, type:
To complete the installation of the above file, you’ll have to set a custom value for the PS1
variable in your .bashrc
file. To do so, open it using nano
(PS1
is a special shell variable used to modify the bash command prompt):
Within that file, there are three lines that begin with PS1. They should be just like these:
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
For each line, insert $(__docker_machine_ps1 " [%s]")
near the end so that they read:
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]$(__docker_machine_ps1 " [%s]")\$ '
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w$(__docker_machine_ps1 " [%s]")\$ '
PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$(__docker_machine_ps1 " [%s]")$PS1"
Save and close the file.
The second script is called docker-machine-wrapper.bash
. It adds a use
subcommand to the docker-machine
command, making it easy to switch between Docker Machines. To download it, type:
The third script is called docker-machine.bash
. It adds bash completion for docker-machine
commands. Download it using:
To apply the changes you’ve made so far, close, then reopen your terminal. If you’re logged into the machine via SSH, exit the session and log in again. Command completion for the docker
and docker-machine
commands should now be working.
Now that you have Docker and Docker Machine running on your local machine, you can now provision a Dockerized Droplet on your DigitalOcean account using Docker Machine’s docker-machine create
command. If you’ve not done so already, assign your DigitalOcean API token to a bash variable using:
NOTE: This tutorial uses DOTOKEN as the bash variable for the DO API token. The variable name does not have to be DOTOKEN, and it does not have to be in all caps.
To make the variable permanent, put it in your ~/.bashrc
file. This step is optional, but it is necessary if you want to the value to persist across terminal sessions.
Open that file with nano
:
Add a line similar to this anywhere:
export DOTOKEN=your-api-token
To activate the variable in the current terminal session, type:
To call the docker-machine create
command successfully you must specify (at a minimum) the driver, the API token (or the variable that evaluates to it), and a unique name for the machine. To create your first machine, type:
Partial output as the machine is being created follows. In this output, the name of the machine is ubuntu1604-docker
:
Output ...
Installing Docker...
Copying certs to the local machine directory...
Copying certs to the remote machine...
Setting Docker configuration on the remote daemon...
Checking connection to Docker...
Docker is up and running!
To see how to connect your Docker Client to the Docker Engine running on this virtual machine, run: docker-machine env ubuntu1604-docker
An SSH key pair is created for the new host so that docker-machine
can access it remotely. The Droplet is provisioned with the desired operating system, and Docker is installed on the system. When the command is complete, your Docker Droplet is up and running.
To see the newly create machine from the command line, type:
The output should be similar to this:
OutputNAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
ubuntu1604-docker - digitalocean Running tcp://203.0.113.71:2376 v18.05.0-ce
By default, the base operating system used when creating a Dockerized host with Docker Machine is supposed to be the latest Ubuntu LTS. However, at the time of this publication, the docker-machine create
command is still using Ubuntu 16.04 LTS as the base operating system, even though Ubuntu 18.04 is the latest LTS edition. So if you need to run Ubuntu 18.04 on a recently-provisioned machine, you’ll have to specify Ubuntu along with the desired version by passing the --digitalocean-image
flag to the docker-machine create
command.
For example, to create a machine using Ubuntu 18.04, type:
You’re not limited to a version of Ubuntu. You can create a machine using any operating system supported on DigitalOcean. For example, to create a machine using Debian 8, type:
To provision a Dockerized host using CentOS 7 as the base OS, specify centos-7-0-x86
as the image name, like so:
The base operating system is not the only choice you have. You can also specify the size of the Droplet. By default, it is the smallest Droplet, which has 1 GB of RAM, a single CPU, and a 25 GB SSD.
Find the size of the Droplet you want to use by looking up the corresponding slug in the DigitalOcean API documentation.
For example, to provision a machine with 2 GB of RAM, two CPUs, and a 60 GB SSD, use the slug s-2vcpu-2gb
:
To see all the flags specific to creating a Docker Machine using the DigitalOcean driver, type:
Tip: If you refresh the Droplet page of your DigitalOcean dashboard, you will see the new machines you created using the docker-machine
command.
You’ve seen how to provision a Dockerized host using the create
subcommand. You also seen how to list the hosts available to Docker Machine using the ls
subcommand. In this step, you’ll learn a few more docker-machine
subcommands.
To obtain detailed information about a Dockerized host, use the inspect
subcommand, like so:
The output should include lines like these. The Image line reveals the version of the Linux distribution used and the size line indicates the size slug:
Output...
{
"ConfigVersion": 3,
"Driver": {
"IPAddress": "203.0.113.71",
"MachineName": "ubuntu1604-docker",
"SSHUser": "root",
"SSHPort": 22,
...
"Image": "ubuntu-16-04-x64",
"Size": "s-1vcpu-1gb",
...
},
---
To print the connection configuration for a host, type:
The output should be similar to this:
Output--tlsverify
--tlscacert="/home/kamit/.docker/machine/certs/ca.pem"
--tlscert="/home/kamit/.docker/machine/certs/cert.pem"
--tlskey="/home/kamit/.docker/machine/certs/key.pem"
-H=tcp://203.0.113.71:2376
The last line in the output of the docker-machine config
command reveals the IP address of the host, but you can also get that piece of information by typing:
If you need to power down a remote host, you can use docker-machine
to stop it:
Verify that it is stopped.
The status of the machine has changed:
OuputNAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
ubuntu1604-docker digitalocean Timeout
To start it again:
Verify that it is started:
You will see that the STATE
is now set Running
for the host:
OuputNAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
ubuntu1604-docker - digitalocean Running tcp://203.0.113.71:2376 v18.05.0-ce
Then you may remove it using:
The Droplet is deleted along with the SSH key created for it by docker-machine.
Now, when you list the Dockerized hosts, you shouldn’t see the one you just deleted:
At this point, you’ve been getting information about your machines, but you can do more than that. For example, you can execute native Linux commands on a Docker host by using the ssh
subcommand of docker-machine
from your local system. This section explains how to perform ssh
commands via docker-machine
as well as how to open an SSH session to a Dockerized host.
Assuming that you’ve provisioned a machine with Ubuntu as the operating system, execute the following command from your local system to update the package database on the Docker host:
You can even apply available updates using:
Not sure what kernel your remote Docker host is using? Type the following:
Besides using the ssh
subcommand to execute commands on the remote Docker host, you can also use it to log into the machine itself. It’s as easy as typing:
Your command prompt will change to reflect the fact that you’re logged into the remote host:
Outputroot@machine-name#
To exit from the remote host, type:
exit
Activating a Docker host connects your local Docker client to that system, which makes it possible to run normal docker
commands on the remote system. To activate a Docker host, type the following command:
Alternatively, you can activate it by using this command:
Tip: When working with multiple Docker hosts, the docker-machine use
command is the easiest method of switching from one to the other.
After typing any of the above commands, your bash prompt should change to indicate that your Docker client is pointing to the remote Docker host. It will take this form. The name of the host will be at the end of the prompt:
username@localmachine:~ [machine-name]$
Now any docker
command you type at this command prompt will be executed on that remote host.
If a host is active on the terminal that the docker-machine ls
command is run, the asterisk under the ACTIVE column shows that it is the active one.
OutputNAME ACTIVE DRIVER STATE URL SWARM DOCKER ERRORS
ubuntu1604-docker * digitalocean Running tcp://203.0.113.71:2376 v18.05.0-ce
To exit from the remote Docker host, type the following:
docker-machine use -u
You will be returned to the prompt for your local system.
Now let’s create containers on the remote machine.
So far, you have provisioned a Dockerized Droplet on your DigitalOcean account and you’ve activated it — that is, your Docker client is pointing to it. The next logical step is to spin up containers on it. As an example, let’s try running the official Nginx container.
Use docker-machine use
to select your remote machine:
Now execute this command to run an Nginx container on that machine:
In this command, we’re mapping port 80
in the Nginx container to port 8080
on the Dockerized host so that we can access the default Nginx page from anywhere.
If the command executed successfully, you will be able to access the default Nginx page by pointing your Web browser to http://docker_machine_ip:8080
.
While the Docker host is still activated (as seen by its name in the prompt), you should be able to list the images on that host:
docker images
The output should include the Nginx image you just used, plus others you downloaded before:
OutputREPOSITORY TAG IMAGE ID CREATED SIZE
nginx latest ae513a47849c 3 weeks ago 109MB
You can also list the active or running containers on the host:
If the Nginx container you ran in this step is the only active container, the output should look like this:
OutputCONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
4284f9d25548 nginx "nginx -g 'daemon of…" 20 minutes ago Up 20 minutes 0.0.0.0:8080->80/tcp httpserver
To exit the prompt for the remote host, type. This will close the terminal as well:
Note: If you intend to create containers on a remote machine, your Docker client must be pointing to it — that is, it must be the active machine in the terminal that you’re using. Otherwise you’ll be creating the container on your local machine. Again, let your command prompt be your guide.
By default, whenever an attempt to provision a Dockerized host using Docker Machine fails or Docker Machine crashes, some diagnostic information is sent automatically to a Docker account on Bugsnag. If you’re not comfortable with this, you can disable the reporting by creating an empty file called no-error-report
in your installation .docker/machine
directory.
To create the file, type:
Check the file for error messages if provisioning fails or Docker Machine crashes.
This has been an introduction to installing and using Docker Machine to provision multiple Docker Droplets remotely from one local system. Now you should be able to quickly provision as many Dockerized hosts on your DigitalOcean account as you need.
For more on Docker Machines, visit the official documentation page. The three Bash scripts downloaded in this tutorial are hosted on this GitHub page.
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This guide appears to be out of date. Not sure if there are any newer ones on this site, but following it and running the command:
resulted in
To fix it, I followed the official Docker guide on DigitalOcean usage with Ubuntu here, using the command:
docker-machine: ‘use’ is not a docker-machine command. See ‘docker-machine --help’.
According to the docs it is not possible to set the project where the droplets will be created. So the default project is used to deploy the droplets on.
Any change it could be set by a preference?
When I run docker-machine create, I get an error. Here’s output with debug turned on. The machine-name is ‘docker-registry’. Command
Error
Earlier in the output I noticed:
When I run just
curl -sSL https://get.docker.com
it tells me the certificate has expired. It seems that is causing docker not to install and the rest to fail.Thanks great article…but how do you connect to your swarm from yet another machine ? i would imagine something like eval $(docker-machine env production-manager-1) but the new machine has no knowledge of what production-manager-1 is.
I followed the steps but it didn’t work at first, I got this when running the
docker-machine create
command:So I created the machine specifying the ubuntu image explicitly:
I got past the error to get this new output:
According to this thread this is apparently related to a version mismatch problem so I provisioned the machined using the command specified in the thread:
After this, the machine got successfully created.
Thank you for the tutorial, it’s very easy to follow and works perfectly.
The only question I have is, which are the outgoing firewall ports that need to be opened up to be able to run ‘docker run…’ from behind the digital ocean cloud firewall?
thanks in advance :)
What is the remote machines initial firewall configuration? Can it be strengthened?
Is it possible to enable private networking while creating a new host?
Thanks for writing this post. Does any one have any tips on resizing a machine provisioned by docker-machine? What are the steps to correctly vertical scale a droplet and making sure it will re-attach to the swarm after resizing?