From: Tom Lane <tgl@sss.pgh.pa.us>
To: Evan Rempel <erempel@uvic.ca>
cc: Chris Hoover <chrish@aweber.com>, pgsql-admin@lists.postgresql.org
Subject: Re: New PG14 server won't start with >2GB shared_buffers
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Comments: In-reply-to Evan Rempel <erempel@uvic.ca>
	message dated "Sat, 25 Feb 2023 07:16:55 -0800"
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Date: Sat, 25 Feb 2023 11:35:17 -0500
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Evan Rempel <erempel@uvic.ca> writes:
> Bear in mind that if you are using systemd to start postgres, then these 
> user limits may not apply.

Yeah, it seems likely that the PG server is being started under
more-restrictive limits than what these manual reports suggest.
It would be useful to try logging in as the Postgres OS user and
manually starting the server -- just do "postgres &" and see what
happens.  (If it does start, "pg_ctl stop" can be used to shut it
down again, or you can manually send SIGTERM to the postmaster
process.)

I tried to reproduce the problem by intentionally setting
"ulimit -v" too small for my PG settings, and I got error messages
that were similar but not identical to what Chris reported.
(I think the sysv case failed at shmat() not shmget().)  So it's
probably not ulimit per se that's responsible.  But if the
server is being started under systemd, then I can entirely
believe that systemd has some poorly-documented feature that
sets additional limits for daemon processes.

I'm still wondering about cgroups, too.

			regards, tom lane