Messages in this thread |  | | From | Christoph Rohland <> | Subject | Re: question about tmpfs | Date | 17 Aug 2001 10:18:46 +0200 |
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On Fri, 17 Aug 2001, safemode@speakeasy.net wrote: > I looked in the documentation for something about tmpfs and looked > around for some obvious tmpfs source but couldn't find any to figure > out how to know when/if it's doing what it's supposed to. when i ls > the dir it's mounted to i get nothing and this is what df gives me. > Filesystem 1k-blocks Used Available Use% Mounted on > tmpfs 144108 0 144108 0% /dev/shm
In the 2.3 timeframe SYSV shared memory did require you to mount shmfs somewhere to work properly. This was relaxed since Al Viro introduced kernel internal mount points. This feature is used now for SYSV shm and shared anonymous maps. You do not see this instance in user space. You can use ipcs to show the SYSV segmants.
The instance on /dev/shm only used by the shmopen/shmunlink functions of glibc 2.2. These functions are specified by POSIX for shared memory handling. Since there aren't a lot of programs using this interface right now, you do not see anything here and could drop this mount from your fstab. But if you use such a program you will need a tmpfs instance mounted somewhere (preferably under /dev/shm).
Greetings Christoph
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