Configuration persistency

By default Elemental and derivatives are reading and executing cloud-init files in (lexicopgrahic) sequence inside:

• /system/oem
• /usr/local/cloud-config
• /oem

It is also possible to run cloud-init file in a different location (URLs included, too) from boot cmdline by using the cos.setup=.. option.

While /system/oem is reserved for system configurations to be included directly in the derivative container image, the /oem folder instead is reserved for persistent cloud-init files that can be extended in runtime.

For example, if you want to change /etc/issue of the system persistently, you can create /usr/local/cloud-config/90_after_install.yaml or alternatively in /oem/90_after_install.yaml with the following content:

# The following is executed before fs is setted up:
stages:
    fs:
        - name: "After install"
          files:
          - path: /etc/issue
            content: |
                    Welcome, have fun!                    
            permissions: 0644
            owner: 0
            group: 0
        - name: "After install (second step)"
          files:
          - path: /etc/motd
            content: |
                    Welcome, have more fun!                    
            permissions: 0644
            owner: 0
            group: 0

For more examples you can find /system/oem inside Elemental vanilla images containing files used to configure on boot a pristine Elemental.