/dev/shm questions??
 

Noticed that Gentoo and Arch recommend using /dev/shm and tmpfs entries in /etc/fstab, as shown below:

They say the 2.6 kernel needs it when using udev.

Have never had any problem with 2.6 and udev w/o these entries, and I am not quite sure what they are for? Do they create an area for shared memory like a dynamic swapfile, ala windows 98 or what?


none /dev/shm tmpfs defaults 0 0
tmpfs /tmp tmpfs defaults 0 0

Thanks,
Gary

I'm not sure exactly I've only used it with qemu emulator but I did a quick google search and it said it was for devfs. udev might still have it for compatability purposes though. The thread I found said it was because glibc 2.2 expected tmpfs to be mounted at /dev/shm. But this was an old lkml posting(6 Apr 2002). But It seems to make sense.

Is it safe to mount /tmp as tmpfs like the fstab lines you posted suggest ?

keefaz,

I think you're right. I was viewing several documents and may have been confused as to whether both tmpfs were needed. Interestingly, when I "df" after running for awhile, it does show about 1% usage on the tmpfs mounted on /tmp. Once when I viewed the contents of /tmp folder, I noticed an alsa file locked, so maybe that was the 1%.

Im going to remove the /tmp line and just leave the /dev/shm mounting point for tmpfs.

I hope someone has a definitive answer as to whether the /dev/shm and tmpfs is recommended for 2.6 kernel and udev or is it just a Gentoo recommendation and a leftover from the soon to be obsolete devfs.

Thanks,
Gary