Here is a site that comes recommended for creating a RAM Disk for Linux. Also I have quoted two members of the Ubuntu community that had some suggestions.
http://www.vanemery.com/Linux/Ramdisk/ramdisk.htmlIf you read this guide, you'll have a RAM disk working easily:
http://www.vanemery.com/Linux/Ramdisk/ramdisk.htmlJust remember some operations require administrative privileges, so put sudo infront of those operations that require it.
rune0077: you can make your ram disk larger / smaller by changing your /boot/grub/menu.lst and adding ramdisk_size=80000 to the end of the kernel line for an 80MB RAM disk (look in the link I gave above).
If you don't specify anything in the /boot/grub/menu.lst, by default you get a 64MB RAM disk.
It's a kernel module (enabled in Ubuntu) that you could use to mount a ram disk. As far as I know the size is static (16 MB), set by the kernel, but it should be possible to change it.
You could take a look over here,
http://www.vanemery.com/Linux/Ramdisk/ramdisk.html(it's old, but I bet the process hasn't changed that much).
This article suggests that you should open /etc/grub.conf:
And in that file add "ramdisk_size=your-size-in-kilobytes" at the end of the line starting with kernel.
