$ initdb -D data-default
The files belonging to this database system will be owned by user "pgsql".
This user must also own the server process.
The database cluster will be initialized with locale "C".
The default database encoding has accordingly been set to "SQL_ASCII".
The default text search configuration will be set to "english".
Data page checksums are disabled.
fixing permissions on existing directory data-default ... ok
creating subdirectories ... ok
selecting default max_connections ... 10
selecting default shared_buffers ... 400kB
selecting dynamic shared memory implementation ... posix
creating configuration files ... ok
creating template1 database in data-default/base/1 ... FATAL: could not create semaphores: Invalid argument
DETAIL: Failed system call was semget(2, 17, 03600).
child process exited with exit code 1
initdb: removing contents of data directory "data-default"
$
$ sysctl -a|grep semm
kern.ipc.semmsl: 512
kern.ipc.semmnu: 256
kern.ipc.semmns: 512
kern.ipc.semmni: 256
The system is running 9.4 just fine and the kernel configuration requirements shouldn't have changed for semaphores.... should they?