ipcs command results always empty

Question

Level 1

75 points

ipcs command results always empty

System V IPC seems to work, but the ipcs command seems broken:

if ( ( i = shmget(k, 0x100000, IPC_CREAT | IPC_EXCL | 0660) ) < 0 ) {
fprintf( stderr, "%s: shmget() error, errno=%d (%s)\n",
argv[0], errno, strerror(errno) );
return(3);
}

$ ./sg a # creates shared memory segment using above code
$ ./sg a # run again, get expected error
./sg: shmget() error, errno=17 (File exists)
$ ipcs
Message Queues:
T ID KEY MODE OWNER GROUP

Shared Memory:
T ID KEY MODE OWNER GROUP

Semaphores:
T ID KEY MODE OWNER GROUP

$

Eventually, I run out of space for shared memory
and have no way to use ipcrm to get rid of these
"test" shared memory regions becasue I cannot
determine the shmid or shmkey because the ipcs
command doesn't provide me with this info.

Suggestions?

-Kurt Lloyd

PowerBook 12" Mac OS X (10.4.4)

Posted on Feb 13, 2006 8:17 AM

Reply

Answer 1

Feb 13, 2006 3:45 PM in response to Kurt Lloyd

You may want to try ipcs -a and see if that gives you the expected results. Apple's shared memory settings are very low. I changed them on my server, some to 512 times the default because of shared memory errors. If you change tune the kernel with /etc/sysctl.conf, check /etc/rc for Apple overriding shm* in /etc/sysctl.conf.

Roger

Reply

Answer 2

Kurt Lloyd Author

Level 1

75 points

Feb 13, 2006 6:18 PM in response to Community User

The only extra thing adding the -a option to the ipcs command does
is add more column headings to an empty dump.
Also, there is no /etc/sysctl.conf file on my system.
And the /etc/rc file contents indicate to me that shared memory is configured:

sysctl -w kern.sysv.shmmax=4194304 kern.sysv.shmmin=1 kern.sysv.shmmni=32 kern.sysv.shmseg=8 kern.sysv.shmall=1024

So I'm still 100% confused.

Reply

Answer 3

Feb 13, 2006 6:29 PM in response to Kurt Lloyd

Have you tried running ipcs as root? either
by logging in a root (su) or via sudo?

Andy

Reply

Answer 4

Kurt Lloyd Author

Level 1

75 points

Feb 13, 2006 6:54 PM in response to Nils C. Anderson

Bingo! Thank you Andy!!

$ ipcs
Message Queues:
T ID KEY MODE OWNER GROUP

Shared Memory:
T ID KEY MODE OWNER GROUP

Semaphores:
T ID KEY MODE OWNER GROUP

$ sudo ipcs
Message Queues:
T ID KEY MODE OWNER GROUP

Shared Memory:
T ID KEY MODE OWNER GROUP
m 131071 1095910432 --rw-rw-rw- root kpl
m 131071 1627522010 --rw-rw---- kpl kpl
m 131071 1644299226 --rw-rw---- kpl kpl
m 262143 1661076442 --rw-rw---- kpl kpl

Semaphores:
T ID KEY MODE OWNER GROUP

$

Reply

Answer 5

Feb 14, 2006 3:55 PM in response to Kurt Lloyd

That was the line in /etc/rc. If you notice, it's right after the rc script goes through /etc/sysctl.conf and appends each line to a sysctl -w command. /etc/sysctl.conf doesn't exist by default, you just have to create it, like /etc/issue.

Roger

Reply