Re: postgresql 18 and shm

[Marc Baudoin <babafou%babafou.eu.org@localhost>]

Patrick Welche <prlw1%welche.eu@localhost> écrit :
> I just tried to upgrade my postgresql 17 database to 18. (NetBSD-11.99.6/amd64)
> 
> run postgresql17
> pg_duamall to somewhere safe
> pkgin remove postgresql17 packages
> pkgin install postgresql18 packages
> zap data directory
> set LANG=C and other LC_ variables to C
> 
> /etc/rc.d/pgsql onestart
> 
> 2026-07-15 09:44:50.670 BST [2380] FATAL:  could not create semaphores: No space left on device
> 2026-07-15 09:44:50.670 BST [2380] DETAIL:  Failed system call was semget(6316451, 17, 03600).
> 2026-07-15 09:44:50.670 BST [2380] HINT:  This error does *not* mean that you have run out of disk space.  It occurs when either the system limit for the maximum number of semaphore sets (SEMMNI), or the system wide maximum number of semaphores (SEMMNS), would be exceeded.  You need to raise the respective kernel parameter.  Alternatively, reduce PostgreSQL's consumption of semaphores by reducing its "max_connections" parameter.

Have a look at this thread from last year:

https://mail-index.netbsd.org/pkgsrc-users/2025/10/25/msg042112.html

The setting that works for me is:

kern.ipc.semmni=20
kern.ipc.semmns=200

I still think changing the default values or, at least,
displaying a warning when installing the package or starting
PostgreSQL with insufficient values would be nice.