I first heard about Rancher back in November 2015. I figured I would give RancherOS another look and see how it’s doing.

RancherOS has an intreguing concept: A base OS that uses Docker containers for everything in the userspace.


  • Rancher OS : A Tiny Linux Distribution designed for running Docker Containers.
  • A novel feature of RancherOS is that it operates all userspace functionality as a Docker container.

wget -o rancher-1.4.1.iso \
  • RancherOS has two Docker Daemons: a system-level and a user-level.
    • The system-docker command is used for accessing and controlling the system-level Docker daemon.
    • The docker command is used for accessing and controlling the user-level Docker daemon.
  • After booting, the system-docker ps command will list all of the system-level Docker containers.

  • Rancher does not have an init system.
  • Any commands to be run on startup must be placed in /opt/rancher/bin/start.sh

Run cAdvisor Docker on the System level

system-docker pull google/cadvisor:latest

system-docker run -d \
  -p 8080:8080 \
  -v /:/rootfs:ro \
  -v /var/run:/var/run:rw  \
  -v /sys:/sys:ro  \
  -v /var/lib/docker/:/var/lib/docker:ro \
  --net=host --name cadvisor google/cadvisor:latest

Install to Disk

  • Boot from the ISO
  • Use the ros install command to install to a disk.
cat << EOF > mycloudconfig.yaml
  - ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDV+7gd7uDd0kxynaFSCjus0NOECHfmADvS1GswNKGYhg4Dd2YMAYPi9OvUgBonrIUYHV8t6mcc6KdpVmuzGGSOfbPgbh+LmQT/7rdCgXDXGNuMBV6J8hDEyV6SPFoMsILAiUX2BPegmfC8F4bdUB4bIoHwm2bR6nEUs1qjPVSqjznS0s4MWzXtcUc7pciDMXYtaJ+NI/LvFfZD/XIrpVaG+JuW8TSDb4pqyMUS9Lkp2UAYKOphwmyZ5vliTv9sGvWyzfAXDe0cTlr1mV71V7YVUc8AMY8GRgaVqGvd4avNLzTmUMkultumFcdQCxZ6gSxBI8QV+kSb+4cWD8oDFbWR devon@Devons-MacBook-Air

fdisk -l /dev/sda
echo -e "o\nw\n" | fdisk /dev/sda
fdisk -l /dev/sda

ros install -c mycloudconfig.yaml -d /dev/sda
  • The cloud-config file will be written to /var/lib/rancher/conf/cloud-config.yml and can be modified any time.
  • After installation, the system will not boot to an interactive console.


  • RancherOS state is controlled by a cloud-config file.
  • On AWS, RancherOS supports loading the cloud-config from the user-data.
  • On-Disk, RancherOS stores the cloud-config data in /var/lib/rancher/conf/cloud-config.yml
  console: ubuntu

  - ssh-rsa AAA...ZZZ example1@rancher
  - ssh-rsa BBB...ZZZ example2@rancher

ros command

  • The ros command is used to edit the configuration of the system
  • To see the DNS configuration of the system: ros config get rancher.network.dns.nameservers
  • Export the current cloud-config: ros config export
  • Validate a cloud-config file: ros config validate -i cloud-config.yml

RancherOS Console

  • The RancherOS console is itself a Docker container.
  • The RancherOS console uses BusyBox by default.
  • The RancherOS console can be switched to another docker-based OS, like Ubuntu.
  • To switch the RancherOS console, use the ros command: ros console switch ubuntu
  • RancherOS Supported Consoles are:
    • default (busybox)
    • alpine
    • centos
    • debian
    • fedora
    • ubuntu
ros console list
ros console switch ubuntu
  • The non-default consoles share /home and /opt with the underlying host, so any changes made there will not be lost between reboots.
categories: rancher | rancheros | docker |