shared memory is not shared

[Donald Kok]

How can I make the shared memory for user ingres rw for group. Thanks in Advance.
Here follows the output from ipcs:

IPC status from /dev/kmem as of Wed Aug 14 11:42:46 2002
T ID KEY MODE OWNER GROUP
Shared Memory:
m 0 0x411c0611 --rw-rw-rw- root root
m 1 0x4e0c0002 --rw-rw-rw- root root
m 2 0x4120036d --rw-rw-rw- root root
m 1803 0x0c6629c9 --rw-r----- root root
m 4 0x06347849 --rw-rw-rw- root root
m 805 0xffffffff --rw-r--rw- root root
m 206 0x331881ab --rw------- root root
m 7 0x6d181009 --rw-rw-rw- root root
m 5008 0xc218a208 --rw------- ingres ingres
m 809 0xc218a209 --rw------- ingres ingres
m 10 0xc218a20a --rw------- ingres ingres
m 1411 0xc218a20c --rw------- ingres ingres
m 12 0xc218a20d --rw------- ingres ingres
m 413 0xc218a20f --rw------- ingres ingres
m 1814 0x00280267 --rw-r--r-- root root

[Deepak Extross · Accepted solution]

Donald,

The program that "creates" the shared memory segment shouldcreate it with the correct permissions.

For example,
shmget (IPC_PRIVATE, 4096, 0600);
would create a 4K shared memory segment with --rw------- permissions. To make it group readable and writable, use
shmget (IPC_PRIVATE, 4096, 0660);

hope this helps.

[A. Clay Stephenson]

If you know any C, it's rather easy using the shmctl() system call BUT normally that's not required unless you are wanting to access the shared memory segments in a way not intended by the designer.

[Sridhar Bhaskarla]

It is to be done during the creation of shared memory segment as mentioned by Deepak. You would need to take it up with the author of the code instead you trying to change it.

-Sri