Re: pg_rewind fails if there is a read only file.

On Tue, 2021-05-25 at 16:57 +0800, Paul Guo wrote:
> > You seem to have missed my point completely. The answer to this problem
> > IMNSHO is "Don't put a read-only file in the data directory".
> 
> Oh sorry. Well, if we really do not want this we may want to document this
> and keep educating users, but meanwhile probably the product should be
> more user friendly for the case, especially considering
> that we know the fix would be trivial and I suspect it is inevitable that some
> extensions put some read only files (e.g. credentials files) in pgdata.

Good idea.  I suggest this documentation page:
https://www.postgresql.org/docs/current/creating-cluster.html

Perhaps something along the line of:

  It is not supported to manually create, delete or modify files in the
  data directory, unless they are configuration files or the documentation
  explicitly says otherwise (for example, <file>recovery.signal</file>
  for archive recovery).

Yours,
Laurenz Albe