ramdisk -- System Administration

Script to create a RAM-disk
/usr/bin/ramdisk

ramdisk is a  script that creates a 500-kilobyte RAM  disk that is accessed
via device /dev/ram0.

To use ramdisk to create a RAM disk for you at boot-time, do the following:

1. Log in as the superuser root.

2. Type:

       touch /dev/ram0close

   This closes the RAM disk and removes it from memory.

3. Remake the ram disk as a smaller size device.  As an example, we'll make
   one that is 64 kilobytes.  Type the command:

       /etc/mknod /dev/ram0 b 8 1

   To break down this command:

   /etc/mknod
        This is  the command  that creates a  special file (e.g.,  a block-
        special  file) through  which a  device  like a  printer or  RAM is
        accessed.

   /dev/ram0
        The directory path and name of your RAM disk.

   b    This  argument tells  mknod to build  a block-special  file.  Every
        device like  a printer, floppy drive, COM port,  or RAM drives, are
        considered a ``block special file.''

   8    This is the major device  number for a RAM drive.  All major-device
        numbers are listed in the Lexicon entry for ``device drivers.''

   1    This is the  minor device number of your new  ram0. This shows that
        the ram0  you are building  will be 64  kilobytes in size.   If the
        minor  device number  would have  been `2', then  the size  of ram0
        would have been two times  64, or 128 kilobytes.  Each increment in
        the minor-device number is  equal to an additional 64 kilobytes for
        the RAM  device.  A minor  device of 16 multiplied  by 64 kilobytes
        would equal a one megabyte size RAM drive.

4. Next, make a file system in ram0:

       /etc/mkfs /dev/ram0 128

   The number  ``128'' is exactly  twice the memory  size, in this  case 64
   kilobytes.  Whatever size memory you choose to allocate to a RAM device,
   the block size  you specify in the mkfs command  will be double.  A one-
   megabyte RAM device for example would have 2,048 blocks.

5. Your new  RAM disk  is now  ready to be  mounted.  Typically,  you would
   mount ram0  in a directory named  fast or some other  unique name, so to
   mount, type;

       /etc/mkdir /fast
       /etc/mount /dev/ram0 /fast

   If /fast already exists, do not create it.

Once  you  have  created your  RAM  disk,  you  should  load commonly  used
utilities into it.

If you wish to create a  RAM disk automatically whenever you boot COHERENT,
un-comment and edit the appropriate lines in file /etc/rc.

See Also

Administering COHERENT,
ram,
rc

Notes

This script only works in machines that have sufficient memory.

© 2012 by Stephen A. Ness