Not sure you should edit it just yet but it shows you have three choices on boot. Do you see those at boot or if you press space bar at boot?
Ignore this "root=/dev/VolGroup00/LogVol00"
Add your ram statement to each if you want to be sure.
This assumes you want it created at boot. I would test within the OS before I went to automation of the disk.
"# mkdir /tmp/ramdisk; chmod 777 /tmp/ramdisk
# mount -t tmpfs -o size=256M tmpfs /tmp/ramdisk/
where 256M is amount of RAM you wish to allocate for ramdisk. It’s clear that this value should be less than amount of free memory (use “free -m“). BTW, if you specify too many MBs for ramdisk Linux will try to allocate it from RAM and then from swap so resulting performance would be very poor."
Here is more what you saw.
I can't say about syg00's statement about tmpfs. May be a better way but no links or suggestions how to use it.