Changing password in Prosody

[Felix Lechner via]

Hi,

How may I change my Prosody password when using the
prosody-service-type, please?

Following the manual, I tried something like

    prosodyctl --config ../../etc/prosody/prosody.cfg.lua passwd JID

but I see errors no matter what I do (chown, chmod).  Sometimes, it's

    "No such file" even though the file exists; or

    "The config file is not readable by the 'prosody' user" even though
    I am root.

Thanks!

Kind regards,
Felix