ramdisks

[Mike Wright]

Oh, great pool of collective wisdom, oracle of all, please be so kind as 
to share your knowledge with me.

I seek knowledge of ramdisks.

1) In /dev there are 16 ramdisks of 16M each.  Are these free for the 
current user or are there other system processes that require them?  If 
they are free to use do I need them to exist if I have no use for them?

2) Where are these created?  I've seen documents that say one may add 
kernel options in grub/lilo to set their size but that implies that they 
all have that same size in common.  Where is their quantity determined?

3) Must they be created during the boot process?


Is there a way to override all of that and create my own layout?  For my 
application I'd rather have two ramdisks, one 10M and the other 30M, 
plus any other(s) that may be required by the o/s.

I tried "mknod /dev/myRamDisk 1 16; chgrp disk /dev/myRamDisk" which, 
while it looks like the other ramdisks in /dev, wasn't available for use.

I looked at tmpfs but that doesn't seem to accomplish what I want.  With 
ramdisks I can mount them over the top of pre-existing directories, play 
to my heart's content, and leave the underlying files untouched.


Wizards, my tia.

Mike Wright :m)