Laurenz Albe <laurenz.albe@cybertec.at> writes:
> It is not a good idea to have a mount point be the data directory.
^^^ This. ^^^
That is primarily for safety reasons: if for some reason the
filesystem gets dismounted, or hasn't come on-line yet during
a reboot, you do not want Postgres to be able to write on the
underlying mount-point directory. There is a sobering tale
in this old thread:
https://www.postgresql.org/message-id/flat/41BFAB7C.5040108%40joeconway.com
Now it didn't help any that they were using a start script that
would automatically run initdb if it didn't see a data directory
where expected. But even without that, you are in for a world of
hurt if the mount drops while the server is running and the server
has any ability to write on the underlying storage; it will think
whatever it was able to write is safely down on disk. To prevent
that, the server must not have write permissions on the mount
point, which dictates making a separate data directory (with
different ownership/permissions) just below the mount.
Do not bypass that ownership/permissions check. It is there
for very good reasons.
regards, tom lane
