citadel/docs/realms.md

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## `default` realm
One realm is always selected to be the `default` realm. The default realm
starts automatically when the system boots. The `realms` utility can be used
to change which realm is the default realm. Switching the default realm changes
the symlink `/realm/default.realm` to point to a different realm instance directory.
citadel:~# realms default
Default Realm: main
citadel:~# realms default project
[+] default realm changed from 'main' to 'project'
citadel:~# realms default
Default Realm: project
## `current` realm
If any realms are running, then one realm is always the `current` realm. The current
realm is a realm that is being monitored by the `citadel-desktopd` daemon. This
daemon is responsible for safely copying application `.desktop` files from the running
realm instance to a temporary directory where they will be read by the GNOME desktop to
to display a menu of applications that can be launched.
Changing the `current` realm, changes the set of applications which are visible to
gnome-shell to only the applications installed in this realm. Also, any applications
started by gnome-shell will run in the `current` realm.
citadel:~# realms
Current Realm: main
## Realms base directory layout
The realms base directory is stored on the storage partition at `/storage/realms` and is bind mounted to `/realms` on the root filesystem for convenience.
/realms
config
/Shared
/skel
/default.realm -> realm-main
/realm-main
/realm-project
/realm-testing
### `/realms/config` file
This file is a template of the configuration file for individual realms. When a new realm is created this file in copied into the new realm instance directory. By modifying this file, the default configuration for new realm instances can be changed.
### `/realms/Shared` directory
This directory is bind mounted to `/home/user/Shared` of each running realm that has the option `use-shared-dir` enabled. It's a convenient way to move files between different realms and between citadel and realms.
### `/realms/skel` directory
Files which are added to this directory will be copied into the home directory of any newly created realm. The directory is copied as a tree of files and may contain subdirectories.
### `/realms/default.realm`
A symlink which points to a realm instance directory of the default realm. The default realm is the realm which starts when the system is booted.
### `/realms/realm-$name`
This is a realm instance directory, for a realm with $name as the realm name.
/realm-main
config
/home
/rootfs
* `config` : configuration file copied from `/realms/config`
* `/home` : directory mounted to `/home/user` in the realm, populated from `/realms/skel`
* `/rootfs` : btrfs subvolume clone (snapshot) of an application image.
### Realm instance directory layout
/realm-main
config
/home
/rootfs