This FAQ answers a few questions about the RAM disks used in the
SnapGear/uClinux distribution.  Specifically,  how to increase
the size of /var/tmp, /etc/config or /tmp.  How to build images
and change the settings as well as some gotchas.

Firstly, if you look in the /etc/rc file on the target
you may see the following:

	/bin/expand /etc/ramfs.img /dev/ram1
	mount -t proc proc /proc
	mount -t ext2 /dev/ram1 /var
	mkdir /var/tmp
	mkdir /var/log
	mkdir /var/run
	mkdir /var/lock

The file ramfs.img is an ext2 file system image that has been compressed.
The expand utility will unpack this into /dev/ram1.
This can then be mounted as an ext2 file system.

This is controlled by the user options specified by the "make menuconfig"
tool, follow this path:

	make menuconfig

	 Target Platform Selection  ---> 
	(enter)
	  [*] Customize Vendor/User Settings (NEW)   
	(exit save options )
	 Miscellaneous Configuration  ---> 
	  (128K) RAMFS Image   <---  ( change the option here )

	exit exit yes
	make dep
	make

And you should have a larger image.  You can easily use images up to
4MiB,  and once you go beyond that you need to increase the RAMdisk
maximum size in the kernel config.

If you do not want all the RAM for the image allocated until you have
filled it with files,  then you need to enable the

	"expand should not write zeroes"

option using the same mechanism above.

If you want to look deeper then the 

	user/ramimage

directory contains more information including a mkrd script that shows
you how to make one of the images.

regards
  Phil Wilshire <philwil@earthlink.net>
  David McCullough <davidm@snapgear.com>