Re: Possibility to disable `ALTER SYSTEM`

Hi,

> I would like to propose a patch that allows administrators to disable `ALTER SYSTEM` via either a runt-time option to
passto the Postgres server process at startup (e.g. `--disable-alter-system=true`, false by default) or a new GUC (or
evenboth), without changing the current default method of the server. 

I'm actually going to put a strong +1 to Gabriele's proposal. It's an
undeniable problem (I'm only seeing arguments regarding other ways the
system would be insecure), and there might be real use cases for users
outside kubernetes for having this feature and using it (meaning
disabling the use of ALTER SYSTEM).

In Patroni for example, the PostgreSQL service is controlled on all
nodes by Patroni, and these kinds of changes could end up breaking the
cluster if there was a failover. For this reason Patroni starts
postgres with some GUC options as CMD arguments so that values in
postgresql.conf or postgresql.auto.conf are ignored. The values in the
DCS are the ones that matter.

```
postgres 1171221  0.0  1.9 903560 55168 ?        S    10:16   0:00
/usr/pgsql-15/bin/postgres -D /opt/postgres/data
--config-file=/opt/postgres/data/postgresql.conf
--listen_addresses=0.0.0.0 --port=5432 --cluster_name=patroni-tpa
--wal_level=logical --hot_standby=on --max_connections=250
--max_wal_senders=6 --max_prepared_transactions=0
--max_locks_per_transaction=64 --track_commit_timestamp=off
--max_replication_slots=6 --max_worker_processes=16 --wal_log_hints=on
```

(see more about how Patroni manages this here:
https://patroni.readthedocs.io/en/latest/patroni_configuration.html#postgresql-parameters-controlled-by-patroni

But let's face it, that's a hack, not something to be proud of, even
if it does what is intended. And this is a product and we shouldn't be
advertising hacks to overcome limitations.

I find the opposition to this lacking good reasons, while I find the
implementation to be useful in some cases.

Kind regards, Martín


--
Martín Marqués
It’s not that I have something to hide,
it’s that I have nothing I want you to see