Hi, like the title implies, I want to ask how to change the size of
"/dev/shm" in openSUSE 10.1? I searched the "/etc/sysconfig/kernel" but there's no
"SHMFS_SIZE" line. I tried "mount -o remount,size=$NEWSIZE /dev/shm" but
it said there's no "/dev/shm" in fstab / mtab. What should I do?

Thanks in advance.

How about using the kernel parameters kernel.shmmax, kernel.shmall, and kernel.shmmax? If you don’t want to pass these to your bootloader, use sysctl.

I've tried that but didn't work. I've tried changing the kernel.shmall & kernel.shmmax to 2 gigs and 4 gigs and rebooted the comp. Then I tried copying 300 megs of files to "/dev/shm" and it said insufficient disk space.

If you changed with sysctl, then rebooted, your changes would be lost… Try changing with sysctl then copying. If you want “permanent” changes, either modify /etc/sysctl.conf or your bootloader’s config file.

Shared memory (/dev/shm) is not used very much so you might not have an entry in fstab. I'm not a memory expert and do not know how shmmax relates to POSIX shared memory or Sys V shared memory but AFAIK tmpfs is dynamic i.e. it will use as much memory as needed until you max out your RAM and swap if a max size not specified. AFAIK /dev/shm is for sharing memory between applications and not used as virtual storage. However you can mount say /tmp as tmpfs.

To specify a max size
tmpfs /dev/shm tmpfs defaults,size=8G 0 0

virtual /tmp directory:
tmpfs /tmp tmpfs defaults 0 0

So what are you trying to accomplish?