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Re: could not create shared memory segment: Invalid argument

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On Tue, Jul 14, 2015 at 8:59 AM, Andy Colson <andy@xxxxxxxxxxxxxxx
<mailto:andy@xxxxxxxxxxxxxxx>> 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



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