Re: Possibility to disable `ALTER SYSTEM`

Hi Joel,

On Wed, 7 Feb 2024 at 10:00, Joel Jacobson <joel@compiler.org> wrote:

On Fri, Sep 8, 2023, at 16:17, Gabriele Bartolini wrote:
> ```
> postgres=# ALTER SYSTEM SET wal_level TO minimal;
> ERROR:  could not open file "postgresql.auto.conf": Permission denied
> ```

+1 to simply mark postgresql.auto.conf file as not being writeable.

To improve the UX experience, how about first checking if the file is not writeable, or catch EACCESS, and add a user-friendly hint?

```
postgres=# ALTER SYSTEM SET wal_level TO minimal;
ERROR:  could not open file "postgresql.auto.conf": Permission denied
HINT: The ALTER SYSTEM command is effectively disabled as the configuration file is set to read-only.
```

This would do - provided we fix the issue with pg_rewind not handling read-only files in PGDATA.

This seems like the simplest solution. And maybe we should be fixing pg_rewind regardless of this issue?

cheers

andrew

--

Andrew Dunstan
EDB: https://www.enterprisedb.com