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Version: 0.6

Filesystem Hierarchy

Here is a quick reference for the filesystem hierarchy:

  • /: Root filesystem (read-write with an overlay).
  • /boot: Boot partition (read-only).
  • /run/rugpi/mounts/config: Config boot partition (usually read-only).
  • /run/rugpi/mounts/system: System partition (read-only).
  • /run/rugpi/mounts/data: Data partition (read-write).
  • /run/rugpi/state: System state (read-write bind mounted).

The state directory /run/rugpi/state is bind mounted to the active state profile on the data partition. Currently, this is always /run/rugpi/data/state/default, however, this will change in the future once the state profile feature lands.

🚧 TODO: The data partition should be better protected against accidental modifications outside of the state directory.

🚧 TODO: The size of the state should be limited to avoid filling the entire data partition. We need some space for the system to boot.

🚧 TODO: Investigate the usage of btrfs instead of ext4 for the data partition. On an SD card (or other low-quality flash memory), we probably do not want to use btrfs due to write amplification increasing the wear on the cells and reducing their lifetime.

Data Partition​

The data partition in /run/rugpi/data has the following hierarchy:

  • overlay/work: Overlay work directory.
  • overlay/root: Overlay root directory.
  • state/default: Default state directory.
  • state/<profile name>: State directory for a given profile (planned).

State​

The state directory /run/rugpi/state has the following hierarchy:

  • overlay/a: A system overlay state.
  • overlay/b: B system overlay state.
  • persist: Files and directories persisted with Rugpi Ctrl.
  • ssh: Persistent SSH host keys.
  • machine-id: Persistent /etc/machine-id.
  • app: Persistent application data.

To persist the data of your application, use Rugpi Ctrl or the app directory.