Hi, I have home assistant OS installed in VM.
I want to access influxdb data directory but I can’t figure out how to do that. I installed SSH addon, logged in, but /data and /mnt directories are empty. As far as I understand I sshed into core, but I need to do that into supervisor/os?
How can I access addon directory?
You aren’t in core. Each addon runs in its own docker container and that includes the ssh addon. You’re sshed into a docker container with the ha cli set up so it can talk to supervisor.
I’m not sure what you’re trying to do but the supported ways of configuring an addon are what is exposed in its configuration options and its user interface. It’s intentional that it’s difficult to get to the data of the container because doing so isn’t supported and can break the addon.
If you need more control then the addon currently provides you should create your own influxdb container from its image on a different system. Or make a new influxdb addon with the options you need.
I want to copy influx data files. And in timescaldb addon you can change some settings only directly in configs of postgresql (as proposed of addon author).
Anyway, is that some sort of secret? 
I tried to find that info by myself, but in my opinion home assistant documentation kind of fragmented and it is hard to see whole picture.
It’s unsupported so therefore undocumented. But if all you want to do is copy files out then easiest way is just to take a backup. Backups without a password are just normal tar files so you can unzip and explore.
If you setup ssh to the host, you can get to it easily.
Then
docker ps
to find the containers.
then
docker exec -it containername <command>
example:
docker exec -it containername bash
Obviously @CentralCommand’s use of the backups is safer. I wouldn’t be monkeying around in the containers. The whole point of HASSIO is to obscure and make it an ‘appliance’ sort of.