Configuring RancherOS

The configuration of RancherOS is on a single configuration file called rancher.yml. You can either use rancherctl config to edit and interact with this file or edit /var/lib/rancher/conf/rancher.yml directly. It is safer to use rancherctl config.

rancherctl

rancherctl is the main command to interact with RancherOS configuration, to the the full documentation.

Networking

RancherOS provides very basic support to get networking up.

network:
  dns:
    nameservers:
      - 8.8.8.8
      - 8.8.4.4
    search:
      - mydomain.com
      - example.com
    domain: mydomain.com
  interfaces:
    eth*:
      dhcp: true
    eth1:
      address: 192.168.0.5
      gateway: 192.168.0.1
      mtu: 1460
    lo:
      address: 127.0.0.1/8

DNS

In the DNS section you can set the nameserver, search, and domain which directly map to the fields of the same name in /etc/resolv.conf

Interfaces

In the interfaces section the keys are used to match the desire interface to configure. Wildcard globbing is supported so eth* will match eth1 and eth2. The available options you can set are address, gateway, mtu, and dhcp.

Cloud Init

cloud_init:
  datasources:
  - configdrive:/media/config-2

In the rancher.yml you can configure which datasources to use for cloud-init. Multiple datasources can be set but the datasource that is available the fastest will be used. This value is usually prepopulated with the current setting for your environment. Valid value are:

configdrive:PATH - Look for an OpenStack compatible config drive mounted at PATH
file:PATH - Read the FILE as the user data.
ec2 - Look for EC2 style meta data at 169.254.169.254
ec2:IP_ADDRESS - Look for EC2 style meta data at the IP_ADDRESS
url:URL - Download URL and use that as the user data
cmdline:URL - Look for cloud-config-url=URL in /proc/cmdline and download URL as user data

Persistence

state:
  fstype: auto
  dev: LABEL=RANCHER_STATE
  autoformat:
  - /dev/sda
  - /dev/vda

RancherOS will store its state in a single partition specified by the dev field. The field can be a device such as /dev/sda1 or a logical name such LABEL=state or UUID=123124. The default value is LABEL=RANCHER_STATE. The file system type of that partition can be set to auto or a specific file system type such as ext4.

Auto formatting

You can specify a list of devices to check to format on boot. If the state partition is already found RancherOS will not try to auto format a partition. If the device specified in autoformat starts with 1 megabyte of zeros, RancherOS will autoformat the parition to ext4. Auto-formatting is off by default.

Upgrades

upgrade:
  url: https://releases.rancher.com/rancheros/versions.yml

The url is used to find the list of available and current versions of RancherOS.

User Docker Configuration

user_docker:
  tls: false
  tls_args: [--tlsverify, --tlscacert=ca.pem, --tlscert=server-cert.pem, --tlskey=server-key.pem,
    '-H=0.0.0.0:2376']
  args: [docker, -d, -s, overlay, -G, docker, -H, 'unix:///var/run/docker.sock']

Configure the user Docker arguments and TLS settings.

System Docker Configuration

system_docker:
  args: [docker, -d, -s, overlay, -b, none, --restart=false, -g, /var/lib/system-docker,
    -H, 'unix:///var/run/system-docker.sock']

Full rancher.yml

The full rancher.yml, including the built in default values in RancherOS can be viewed by running rancherctl config export --full. Below is the output of the full yaml file.

addons:
  ubuntu-console:
    system_containers:
    - id: console
      run: --name=ubuntu-console -d --rm --privileged --volumes-from=all-volumes --restart=always
        --ipc=host --net=host --pid=host rancher/ubuntuconsole:v0.0.2
bootstrap_containers:
- id: udev
  run: --name=udev --net=none --privileged --rm -v=/dev:/host/dev -v=/lib/modules:/lib/modules:ro
    udev
cloud_init:
  datasources:
  - configdrive:/media/config-2
network:
  dns:
    nameservers: [8.8.8.8, 8.8.4.4]
  interfaces:
    eth*:
      dhcp: true
    lo:
      address: 127.0.0.1/8
state:
  fstype: auto
  dev: LABEL=RANCHER_STATE
  autoformat:
  - /dev/sda
  - /dev/vda
system_docker:
  args: [docker, -d, -s, overlay, -b, none, --restart=false, -g, /var/lib/system-docker,
    -H, 'unix:///var/run/system-docker.sock']
upgrade:
  url: https://cdn.rancher.io/rancheros/versions.yml
user_docker:
  tls_args: [--tlsverify, --tlscacert=ca.pem, --tlscert=server-cert.pem, --tlskey=server-key.pem,
    '-H=0.0.0.0:2376']
  args: [docker, -d, -s, overlay, -G, docker, -H, 'unix:///var/run/docker.sock']

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