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Tutorial
How To Provision and Manage Remote Docker Hosts with Docker Machine on Ubuntu 16.04
Not using Ubuntu 16.04 ? Choose a different version or distribution.
Ubuntu 16.04
Introduction
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.
Prerequisites
To follow this tutorial, you will need the following:
Step 1 — Installing Docker Machine on Your Local Computer
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:
- wget https://github.com/docker/machine/releases/download/v0.14.0/docker-machine-$(uname -s)-$(uname -m)
The name of the file should be
docker-machine-Linux-x86_64. Rename it todocker-machineto make it easier to work with:
- mv docker-machine-Linux-x86_64 docker-machine
Make it executable:
- chmod +x docker-machine
Move or copy it to the
usr/local/bindirectory so that it will be available as a system command.
- sudo mv docker-machine /usr/local/bin
Check the version, which will indicate that it’s properly installed:
- docker-machine version
The output should be similar to
Step 2 — Installing Additional Docker Machine Scripts
There are three bash scripts in the Docker Machine GitHub repository designed to facilitate the usage of the
dockeranddocker-machinecommands. 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.ddirectory.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:
- sudo wget https://raw.githubusercontent.com/docker/machine/master/contrib/completion/bash/docker-machine-prompt.bash -O /etc/bash_completion.d/docker-machine-prompt.bash
To complete the installation of the above file, you’ll have to set a custom value for the
PS1variable in your.bashrcfile. To do so, open it usingnano(PS1is a special shell variable used to modify the bash command prompt):
- nano ~/.bashrc
Within that file, there are three lines that begin with PS1. They should be just like these:
~/.bashrcPS1='${debian_chroot:+($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
$(__docker_machine_ps1 " [%s]")near the end so that they read:~/.bashrcPS1='${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 ausesubcommand to thedocker-machinecommand, making it easy to switch between Docker Machines. To download it, type:
- sudo wget https://raw.githubusercontent.com/docker/machine/master/contrib/completion/bash/docker-machine-wrapper.bash -O /etc/bash_completion.d/docker-machine-wrapper.bash
The third script is called
docker-machine.bash. It adds bash completion fordocker-machinecommands. Download it using:
- sudo wget https://raw.githubusercontent.com/docker/machine/master/contrib/completion/bash/docker-machine.bash -O /etc/bash_completion.d/docker-machine.bash
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
dockeranddocker-machinecommands should now be working.Step 3 — Provisioning a Dockerized Host Using Docker Machine
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 createcommand. If you’ve not done so already, assign your DigitalOcean API token to a bash variable using:
- export DOTOKEN=your-api-token
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
~/.bashrcfile. This step is optional, but it is necessary if you want to the value to persist across terminal sessions.Open that file with
nano:
- nano ~/.bashrc
Add a line similar to this anywhere:
~/.bashrcexport DOTOKEN=your-api-tokenTo activate the variable in the current terminal session, type:
- source ~/.bashrc
To call the
docker-machine createcommand 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:
- docker-machine create --driver digitalocean --digitalocean-access-token $DOTOKEN machine-name
Partial output as the machine is being created follows. In this output, the name of the machine is
ubuntu1604-docker:An SSH key pair is created for the new host so that
docker-machinecan 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:
- docker-machine ls
The output should be similar to this:
Step 4 — Specifying the Base OS When Creating a Dockerized Host
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 createcommand 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-imageflag to thedocker-machine createcommand.For example, to create a machine using Ubuntu 18.04, type:
- docker-machine create --driver digitalocean --digitalocean-image ubuntu-18-04-x64 --digitalocean-access-token $DOTOKEN machine-name
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:
- docker-machine create --driver digitalocean --digitalocean-image debian-8-x64 --digitalocean-access-token $DOTOKEN machine-name
To provision a Dockerized host using CentOS 7 as the base OS, specify
centos-7-0-x86as the image name, like so:
- docker-machine create --driver digitalocean --digitalocean-image centos-7-0-x64 --digitalocean-access-token $DOTOKEN centos7-docker
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:You’ve seen how to provision a Dockerized host using the
createsubcommand. You also seen how to list the hosts available to Docker Machine using thelssubcommand. In this step, you’ll learn a few moredocker-machinesubcommands.To obtain detailed information about a Dockerized host, use the
inspectsubcommand, like so:
- docker-machine inspect machine-name
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:
To print the connection configuration for a host, type:
- docker-machine config machine-name
The output should be similar to this:
The last line in the output of the
docker-machine configcommand reveals the IP address of the host, but you can also get that piece of information by typing:
- docker-machine ip machine-name
If you need to power down a remote host, you can use
docker-machineto stop it:
- docker-machine stop machine-name
Verify that it is stopped.
- docker-machine ls
The status of the machine has changed:
To start it again:
- docker-machine start machine-name
Verify that it is started:
- docker-machine ls
You will see that the
STATEis now setRunningfor the host:Then you may remove it using:
- docker-machine rm machine-name
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:
- docker-machine ls
Step 6 — Executing Commands on a Dockerized Host via SSH
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
sshsubcommand ofdocker-machinefrom your local system. This section explains how to performsshcommands viadocker-machineas 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:
- docker-machine ssh machine-name apt-get update
You can even apply available updates using:
- docker-machine ssh machine-name apt-get upgrade
Not sure what kernel your remote Docker host is using? Type the following:
- docker-machine ssh machine-name uname -r
Besides using the
sshsubcommand 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:
- docker-machine ssh machine-name
Your command prompt will change to reflect the fact that you’re logged into the remote host:
To exit from the remote host, type:
Step 7 — Activating a Dockerized Host
Activating a Docker host connects your local Docker client to that system, which makes it possible to run normal
dockercommands on the remote system. To activate a Docker host, type the following command:
- eval $(docker-machine env machine-name)
Alternatively, you can activate it by using this command:
- docker-machine use machine-name
Tip: When working with multiple Docker hosts, the
docker-machine usecommand is the easiest method of switching from one to the other.After typing any of the above commands, your bash prompt should change to indicate that your Docker client is pointing to the remote Docker host. It will take this form. The name of the host will be at the end of the prompt:
username@localmachine:~ [machine-name]$Now any
dockercommand 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 lscommand is run, the asterisk under the ACTIVE column shows that it is the active one.To exit from the remote Docker host, type the following:
docker-machine use -uYou will be returned to the prompt for your local system.
Now let’s create containers on the remote machine.
Step 8 — Creating Docker Containers on a Remote Dockerized Host
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 useto select your remote machine:
- docker-machine use machine-name
Now execute this command to run an Nginx container on that machine:
- docker run -d -p 8080:80 --name httpserver nginx
In this command, we’re mapping port
80in the Nginx container to port8080on 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 imagesThe output should include the Nginx image you just used, plus others you downloaded before:
You can also list the active or running containers on the host:
- docker ps
If the Nginx container you ran in this step is the only active container, the output should look like this:
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.
Step 9 — Disabling Crash Reporting (Optional)
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-reportin your installation.docker/machinedirectory.To create the file, type:
- touch ~/.docker/machine/no-error-report
Check the file for error messages if provisioning fails or Docker Machine crashes.
Conclusion
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.
Thanks for learning with the DigitalOcean Community. Check out our offerings for compute, storage, networking, and managed databases.
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callumjhays • April 6, 2017This 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:maxtr • June 26, 2016docker-machine: ‘use’ is not a docker-machine command. See ‘docker-machine --help’.Mark Veenstra • July 26, 2019According 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?
Kip Obenauf • June 2, 2018When I run docker-machine create, I get an error. Here’s output with debug turned on. The machine-name is ‘docker-registry’. Commandmikkel418725b8766e1a77ce54 • April 9, 2018Thanks 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.ceroso398 • March 25, 2018I followed the steps but it didn’t work at first, I got this when running thedocker-machine createcommand:christiangiacomi • July 25, 2017Thank you for the tutorial, it’s very easy to follow and works perfectly.