[RndTbl] /dev/shm

Sean A. Walberg sean at ertw.com
Wed Jul 21 06:49:52 CDT 2004


On Tue, 2004-07-20 at 23:02, Mike Pfaiffer wrote:
> 	What is /dec/shm? Is is kind of a RAM drive? I have had an entry in my df 

[sean at bob sean]$ mount
...
none on /dev/shm type tmpfs (rw)

[sean at bob sean]$ locate tmpfs
/usr/src/linux-2.4.22-1.2188.nptl/include/config/tmpfs.h
/usr/src/linux-2.4.22-1.2197.nptl/Documentation/filesystems/tmpfs.txt
/usr/src/linux-2.4.22-1.2197.nptl/fs/intermezzo/journal_tmpfs.c

[sean at bob sean]$ more
/usr/src/linux-2.4.22-1.2197.nptl/Documentation/filesystems/tmpfs.txt
Tmpfs is a file system which keeps all files in virtual memory.
...

Who uses it?  shm is an acronym for SHared Memory.  From the shm_open(3)
man page there is a note:

>  The POSIX shared memory object implementation on Linux 2.4 makes use
>  of a dedicated file system, which is normally mounted under /dev/shm.

"UNIX Network Programming" by Stevens explains shm and other forms of
IPC far better than I could ever hope to.

Sean






-- 
Sean A. Walberg <sean at ertw.com>                 http://www.ertw.com





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