If you have a specific RanchersOS machine requirements, please check out our guides on running RancherOS. With the rest of this guide, we’ll start up a RancherOS using Docker machine and show you some of what RancherOS can do.

Launching RancherOS using Docker Machine

Before moving forward, you’ll need to have Docker Machine and VirtualBox installed. Once you have VirtualBox and Docker Machine installed, it’s just one command to get RancherOS running.

$ docker-machine create -d virtualbox \
        --virtualbox-boot2docker-url https://releases.rancher.com/os/latest/rancheros.iso \
        --virtualbox-memory 2048 \
        <MACHINE-NAME>

That’s it! You’re up and running a RancherOS instance.

To log into the instance, just use the docker-machine command.

$ docker-machine ssh <MACHINE-NAME>

A First Look At RancherOS

There are two Docker daemons running in RancherOS. The first is called System Docker, which is where RancherOS runs system services like ntpd and syslog. You can use the system-docker command to control the System Docker daemon.

The other Docker daemon running on the system is Docker, which can be accessed by using the normal docker command.

When you first launch RancherOS, there are no containers running in the Docker daemon. However, if you run the same command against the System Docker, you’ll see a number of system services that are shipped with RancherOS.

Note: system-docker can only be used by root, so it is necessary to use the sudo command whenever you want to interact with System Docker.

$ sudo system-docker ps
CONTAINER ID        IMAGE                       COMMAND                  CREATED             STATUS              PORTS               NAMES
6f56057cf5ba        rancher/os-base:v0.5.0      "/usr/sbin/entry.sh /"   16 seconds ago      Up 15 seconds                           docker
bd5376830237        rancher/os-console:v0.5.0   "/usr/sbin/entry.sh /"   16 seconds ago      Up 15 seconds                           console
ede8ce39fff5        rancher/os-base:v0.5.0      "/usr/sbin/entry.sh n"   16 seconds ago      Up 15 seconds                           network
9e5d18bca391        rancher/os-base:v0.5.0      "/usr/sbin/entry.sh n"   17 seconds ago      Up 16 seconds                           ntp
393b9fb7e30a        rancher/os-udev:v0.5.0      "/usr/sbin/entry.sh /"   18 seconds ago      Up 16 seconds                           udev
dc2cafca3c69        rancher/os-syslog:v0.5.0    "/usr/sbin/entry.sh /"   18 seconds ago      Up 17 seconds                           syslog
439d5535fbfa        rancher/os-base:v0.5.0      "/usr/sbin/entry.sh /"   18 seconds ago      Up 17 seconds                           acpid

Some containers are run at boot time, and others, such as the console, docker, etc. containers are always running.

Using RancherOS

Deploying a Docker Container

Let’s try to deploy a normal Docker container on the Docker daemon. The RancherOS Docker daemon is identical to any other Docker environment, so all normal Docker commands work.

$ docker run -d nginx

You can see that the nginx container is up and running:

$ docker ps
CONTAINER ID        IMAGE               COMMAND                  CREATED             STATUS              PORTS               NAMES
e99c2c4b8b30        nginx               "nginx -g 'daemon off"   12 seconds ago      Up 11 seconds       80/tcp, 443/tcp     drunk_ptolemy

Deploying A System Service Container

The following is a simple Docker container to set up Linux-dash, which is a minimal low-overhead web dashboard for monitoring Linux servers. The Dockerfile will be like this:

FROM hwestphal/nodebox
MAINTAINER [email protected]

RUN opkg-install unzip
RUN curl -k -L -o master.zip https://github.com/afaqurk/linux-dash/archive/master.zip
RUN unzip master.zip
WORKDIR linux-dash-master
RUN npm install

ENTRYPOINT ["node","server"]

Using the hwestphal/nodebox image, which uses a Busybox image and installs node.js and npm. We downloaded the source code of Linux-dash, and then ran the server. Linux-dash will run on port 80 by default.

To run this container in System Docker use the following command:

$ sudo system-docker run -d --net=host --name busydash husseingalal/busydash

In the command, we used --net=host to tell System Docker not to containerize the container’s networking, and use the host’s networking instead. After running the container, you can see the monitoring server by accessing http://<IP_OF_MACHINE>.

System Docker Container

To make the container survive during the reboots, you can create the /opt/rancher/bin/start.sh script, and add the Docker start line to launch the Docker at each startup.

$ sudo mkdir -p /opt/rancher/bin
$ echo "sudo system-docker start busydash" | sudo tee -a /opt/rancher/bin/start.sh
$ sudo chmod 755 /opt/rancher/bin/start.sh

Using ROS

Another useful command that can be used with RancherOS is ros which can be used to control and configure the system.

$ sudo ros -v
ros version 0.0.1

RancherOS state is controlled by a cloud config file. ros is used to edit the configuration of the system, to see for example the dns configuration of the system:

$ sudo ros config get rancher.network.dns.nameservers
- 8.8.8.8
- 8.8.4.4

When using the native Busybox console, any changes to the console will be lost after reboots, only changes to /home or /opt will be persistent. You can use the ros console switch command to switch to a persistent console and replace the native Busybox console. For example, to switch to the Ubuntu console:

$ sudo ros console switch ubuntu

Conclusion

RancherOS is a simple Linux distribution ideal for running Docker. By embracing containerization of system services and leveraging Docker for management, RancherOS hopes to provide a very reliable, and easy to manage OS for running containers.