Im reallty looking forward homebridge in hassio
For persistant data storage inside add-on, you can use /data. That is a private storage per add-on otherwise /share that can be available on ever addon and is also mount to homeassistant. /data will be also auto cleanup on uninstall of add-on.
I would like to add tmpfs capability to the addons. It is relatively trivial to add a new dictionary in config.json to use the tmpfs option on the docker api. I could propose a PR in github if you think you can integrate it.
Adding this option to addons config is needed to prevent multiple write on the sd card when it is not needed. I will use it for the pipe file between mopidy and snapcast.
Ok, I see not mutch case who that is needed but I donāt see any security problems. Yes please make PR. I will cleanup the docker code, but I wait until your PR is done.
Why canāt you use /dev/shm as mentioned in https://unix.stackexchange.com/questions/26364/how-can-i-create-a-tmpfs-as-a-regular-non-root-user ?
I didnāt know that one. Thanks ! With the tmpfs option it is possible to specify the size limit, which is not possible with /dev/shm. But it is another possibility I will keep in mind.
EDIT : /dev/shm is a mount point, and not a device :
docker: Error response from daemon: linux runtime spec devices: error gathering device information while adding custom device "/dev/shm": not a device node.
Should I put Homebridge config in /share? As a user, I like the idea of having all my configs in the same folder (/config).
Loosely related: where are the add-ons configs stored? Is there a way to back them up or restore them all at once? Something like /config/addons/addon_slug.json or /config/addons/addon_slug/config.json would be nice 
Then, it would maybe be cleaner to move HA config folder from /config to /config/homeassistant.
Addon data/config are in /data. Addons should be have only options they are available over the UI. In your case, you should setup the homebridge config from options every startup like the core addons does.
I thought about that, but the config file of homebridge can be very complex, depending on the installed plugins. Is it possible to say we accept āany valid JSONā under one or more fields of the add-on config? The current schema property doesnāt seem to allow that.
In addition, I would like users to be able to access the persist folder of homebridge as itās useful for backups (and debug).
In next hass.io release you can use schema: false and use any json for options.
Backup/restore will be a core feature in few weeks and work with /data too. Anyway it is your addon repository and you can do what you want do.
Thanks for your answer Glad to hear backup/restore will be core features!
I wanna be a good citizen of the platform, Iāll update my add-on then to take advantage of them and place the config/persistance files correctly.