Today’s computer world is experiencing a new concept of thinking apps and how to deploy them. Old application practices were focused on stacks created over a complete machine (phisical or virtual). This approach has demonstrated to lead some concerns regarding resources use, infra-application conflicts and poor development flexibility management.
Containers have born to help developers and system administrators to help in this sense. Docker has become the most known company who implemented this concept. As defined in Docker website: “A container image is a lightweight, stand-alone, executable package of a piece of software that includes everything needed to run it: code, runtime, system tools, system libraries, settings. Available for both Linux and Windows based apps, containerized software will always run the same, regardless of the environment. Containers isolate software from its surroundings, for example differences between development and staging environments and help reduce conflicts between teams running different software on the same infrastructure.” (Ref. https://www.docker.com/what-container).
But using containers alone may require advanced knowledge. For this reason a good hand is given by another company: Rancher. Rancher is “open source software that combines everything an organization needs to adopt and run containers in production. Built on Kubernetes, Rancher makes it easy for DevOps teams to test, deploy and manage their applications. Operations teams use Rancher to deploy, manage and secure every Kubernetes deployment regardless of where it is running.“.
Now, what if we try to use them togheter over a consumer grade hardware? In this article we will try it on a Raspberry PI 3 model B.
What we need
- At least Raspberry PI 3 model B kit (including at least also case, USB adapater and power supply)
- 1 micro SD card (at least 8 GB, preferrably class 10) with an SD adapter
- 1 HDMI cable
- a USB/wireless keyboard
- a network cable to connect your Raspberry to your router
- rancheros raspberry pi64 image (you can download it from here, I’m going to use version v1.5.3)
- an image flashing software like, for example, Etcher
- a remote ssh software (like Putty if you’re working from a Windows remote PC)
Download and install in your PC Etcher.
Download rancherOS zip file in your computer and extract .img file locally.
Run Etcher in your PC.
Click over Select Image and select RancherOS image previously downloaded. Now Etcher should also have recognised your SD card. Otherwise, click change and select correct SD card.
Click on “Flash! button and wait for operation to be completed
Now you can insert SD card in your Raspberry, connect your network cable and boot it.
Login using default user “rancher” and default password “rancher”.
As warned by old RancherOS installation guide, it does not currently expand the root partition to fill the entire SD card automatically. Instead, the following workaround can be used to store Docker containers on a larger partition that fills the remaining space.
sudo fdisk /dev/mmcblk0
when it prompts:
- press “n” to create a new partition
- press ENTER 4 times to accept default settings for new partition
- press “w” to write the table and exit
an alert message will warn you that system needs a reboot in order to apply new configuration. so, let’s reboot:
After reboot, re-connect to your raspberry:
create the directory to be used as the new Docker root:
sudo mkdir /mnt/docker
configure Docker to use the new root:
sudo ros config set rancher.docker.extra_args [-g,/mnt/docker]
format the disk:
sudo mkfs.ext4 /dev/mmcblk0p3
preserve this mount after reboots:
sudo ros config set mounts "[['/dev/mmcblk0p3','/mnt/docker','ext4','']]"
mount the Docker root:
sudo mount /dev/mmcblk0p3 /mnt/docker
restart Docker using the new root:
sudo system-docker restart docker
With RancherOS version 1.5 the WiFi support has been implemented. From terminal you will need to edit the cloud-config.yml file to enable WiFi. The only text editor available is VI, so you need to understand the basis of this editor (just how to edit a file and hot to quit and save) to configure WiFi.
Let’s start from editing the file:
sudo vi /var/lib/rancher/conf/cloud-config.yml
then you must find rancher section and manually add the network group so that your file appear something similar to the following:
rancher: docker: extra_args: - -g - /mnt/docker network: interfaces: wlan0: wifi_network: network1 wifi_networks: network1: psk: <<your-wifi-password>> ssid: <<your-wifi-ssid>>
Restart network service:
sudo system-docker restart network
and check with ifconfig command that wlan0 has correctly an IP address assigned. If so, you can now connect from your favourite remote ssh software.
Enable a persistent console
Switch to a persistent console (for example ubuntu):
sudo ros console switch ubuntu
Now docker is ready and running.
A graceful web GUI helping in managing containers is portainer. In our case, we need to install an arm compatible version:
sudo docker pull portainer/portainer:linux-arm docker run -d -p 9000:9000 -v /var/run/docker.sock:/var/run/docker.sock -v portainer_data:/data portainer/portainer:linux-arm
Now you can reach your docker server with a browser, just connecting to https://<<RaspberryIpAddress>>:9000.
You will be required to set your default password for admin user, then you will be prompted to portainer GUI: