use shmfs

use shmfs

[Hua Zhong]

Hi:

Currently I'm using shmfs as a volatile storage. I am using Monta Vista's
kernel (2.4.2). I added the following line in /etc/fstab:

tmpfs                   /dev/shm                shm     defaults        0 0

# df /dev/shm
Filesystem           1k-blocks      Used Available Use% Mounted on
tmpfs                        0         0         0   -  /dev/shm

the "0" number of blocks seems fishy.

I cannot write to the filesystem. write returns EINVAL. I can create an
empty file, however.

What should I do to make it work? Thanks.

By the way, I know tmpfs is a replacement of shmfs, but it's not in the
2.4.2 kernel I am using (can't find in config). Is it in any newer kernels
(especially 2.4.9)? Is it stable enough?

Thanks

Re: use shmfs

[Robert Love]

On Sat, 2001-12-15 at 19:26, Hua Zhong wrote:

> Currently I'm using shmfs as a volatile storage. I am using Monta Vista's
> kernel (2.4.2). I added the following line in /etc/fstab:
> 
> tmpfs                   /dev/shm                shm     defaults        0 0
> <snip>
> I cannot write to the filesystem. write returns EINVAL. I can create an
> empty file, however.

It is confusing: tmpfs is used both for abstracting POSIX shared memory
(shm) and for a page-cache-based dynamic RAM disk.  The line above, that
you are adding, is for the shm support.  You need to add another line to
create the tmpfs filesystem at a given mount point.  Example:

tmpfs		/var/cheese	tmpfs	defaults,size=4m	0 0

Would create a tmpfs at /var/cheese.  The (optional) size parameter
specifies a maximum fs size of 4MB.

See Documentation/filesystems/tmpfs.txt for more information.

	Robert Love