Rancher OS is a very lightweight Linux distribution built around Docker. The OS itself weighs in around 20MB. This tutorial will get you up and running with a persistent Rancher OS using all of the available disk space. Cloud-config instructions are not included in this doc.
Create a new Custom PXE start up script and name it RancherOS.
Paste in the script template below.
Generate a new secure password and replace CHANGETHIS.
Save the script.
Deploy a new server using the ISO Custom option and select iPXE and your new RancherOS script from the dropdown.
Wait several minutes for the installation to complete.
Login with rancher@xxx.xxx.xxx.xxx and your new password.
Setup is complete. At this point you can start configuring your rancher server or bootstrap it server to another rancher server.
#!ipxe
# Boots RancherOS in Ramdisk with persistent storage on disk /dev/vda
# Location of Kernel/Initrd images
set base-url http://releases.rancher.com/os/latest
kernel ${base-url}/vmlinuz rancher.state.dev=LABEL=RANCHER_STATE rancher.state.autoformat=[/dev/vda] rancher.password=CHANGETHIS
initrd ${base-url}/initrd
boot
While setting the rancher.password kernel parameter works, the Rancher team advises not doing this in production. Kernel parameters will be readable by any container launched, including unprivileged ones. A better method would be to add an SSH key via cloud-config. Specifying a cloud-config file is done by adding a kernel parameter. An example of this parameter is shown below. You would need to replace the URL in the parameter to the location of your cloud-config file.
rancher.cloud_init.datasources=[url:http://example.com/cloud-config]
Here is an example cloud-config file template that includes SSH keys. This file is in YAML format. Replace the SSH keys in the template with one or more of your own keys.
#cloud-config
ssh_authorized_keys:
- ssh-rsa AAA...ZZZ example1@rancher
- ssh-rsa BBB...ZZZ example2@rancher
More information on using cloud-config with Rancher OS is provided in the official documentation.