Message-ID: <55A515B4.1080903@squeakycode.net>
Date: Tue, 14 Jul 2015 08:59:16 -0500
From: Andy Colson <andy@squeakycode.net>
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To: Ryan King - NOAA Affiliate <ryan.king@noaa.gov>,
 pgsql-general@postgresql.org
Subject: Re: could not create shared memory segment: Invalid argument
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On 7/13/2015 7:08 PM, Ryan King - NOAA Affiliate wrote:
> Apologies ahead of time for not knowing which group to send to, but I
> wanted to see if anyone has encountered and resolved this type of error.
> I'm setting up postgresql 9.2 streaming replication on RH and after
> copying the master data directory over to the slave, the psql service
> refuses start and gives the following errors.
>
>
>
>     2015-07-13 23:55:41.224 UTC FATAL:  could not create shared memory
> segment: Invalid argument
>     2015-07-13 23:55:41.224 UTC DETAIL:  Failed system call was
> shmget(key=5432001, size=1146945536, 03600).
>     2015-07-13 23:55:41.224 UTC HINT:  This error usually means that
> PostgreSQL's request for a shared memory segment exceeded your kernel's
> SHMMAX parameter.  You can either reduce the request size or reconfigure
> the kernel with larger SHMMAX.  To reduce the request size (currently
> 1146945536 bytes), reduce PostgreSQL's shared memory usage, perhaps by
> reducing shared_buffers or max_connections.
>          If the request size is already small, it's possible that it is
> less than your kernel's SHMMIN parameter, in which case raising the
> request size or reconfiguring SHMMIN is called for.
>          The PostgreSQL documentation contains more information about
> shared memory configuration.
>     2015-07-13 23:56:21.344 UTC FATAL:  could not create shared memory
> segment: Invalid argument
>     2015-07-13 23:56:21.344 UTC DETAIL:  Failed system call was
> shmget(key=5432001, size=58302464, 03600).
>     2015-07-13 23:56:21.344 UTC HINT:  This error usually means that
> PostgreSQL's request for a shared memory segment exceeded your kernel's
> SHMMAX parameter.  You can either reduce the request size or reconfigure
> the kernel with larger SHMMAX.  To reduce the request size (currently
> 58302464 bytes), reduce PostgreSQL's shared memory usage, perhaps by
> reducing shared_buffers or max_connections.
>          If the request size is already small, it's possible that it is
> less than your kernel's SHMMIN parameter, in which case raising the
> request size or reconfiguring SHMMIN is called for.
>          The PostgreSQL documentation contains more information about
> shared memory configuration.
>
>
>
> I've set shared_buffer way down to next to nothing along with
> kernel.shmmax and kernel.shmall per some blogs. However, the same error
> persists, and I'm getting no where. I think ultimately the solution is
> to upgrade, but the devs may not be ready for an upgrade at this point.
> Any help would be greatly appreciated. Thanks!

You don't want to decrease kernel.shmmax you want to set it to the 
request size:

sysctl -w kernel.shmmax=1146945536

shmmax is the only thing you really need to play with.

-Andy


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