Re: could not create shared memory segment: Invalid argument - Mailing list pgsql-general

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