Re: could not create shared memory segment: Invalid argument

> On Tue, Jul 14, 2015 at 8:59 AM, Andy Colson <andy(at)squeakycode(dot)net
> <mailto:andy(at)squeakycode(dot)net>> wrote:
>
> 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
>
>

On 7/15/2015 9:13 AM, Ryan King - NOAA Affiliate wrote:
> I tried that too - same result. I updated another box w/ the same issue
> to 9.4.4, and all is well there. Thanks for your reply.
>

Ah, I assume then that something else is already using some shared memory.

PG needs:
> To reduce the request size (currently 58302464 bytes),

That much shared memory *free*. You can check current usage with: ipcs -m

Add what PG needs to what you are already using, and you should be good
to go.

-Andy