fast mapcalc

Tom Moore tmoore at
Tue Jul 4 08:00:00 EDT 1995

In mailgate.grass.user you write:

>OK smart fellas, show me!  Name four major commercial Unix systems with
>"ram-disk" and specifics about mounting procedures.
>I can verify on Sun OS, a couple of DEC flavors, SVR4.  Reference to
>"man" pages acceptable.

I don't know about anything other than SunOS and Linux, but there
are memory based file systems for both of these OS.  Linux
has already been mentioned.   For SunOS 4.1.3 see the man page
for tmpfs.

Virtual memory file systems have been around for a long, long
time.  In my IBM s/370 MVS days there was a JCL parameter
for "disk=vio" which would allocate space for the file in virtual
memory.  This was over 15 years ago.

Under Linux and SunOS 4.1.3 the memory based file systems behave
just like disk based file systems.  The same concept of access
permissions and file sharing applies.  All of the usual disk management
commands (ls, cp, mkdir, rm, chmod, chown ....) work as normal.

As was mentioned in an earlier post, root access is required to
create and attach file systems (unless you are running an unusually
lax system).  You also need to have the file system drivers loaded
into the kernel.  

Tom Moore R.P.F.                                tmoore at
Petawawa National Forestry Institute            
Canadian Forest Service, Box 2000, Chalk River  +1 (613) 589-3048
ONT K0J 1J0  CANADA                             +1 (613) 589-2275 telefax

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