RAMDISK is part of system memory which user can use as a normal disk space. The advantage of RAMDISK is faster read and write access in comparison of Hard Disk.
By default Ubuntu mounts RAMDISK on /dev/shm/ directory.
To setup RAMDISK on other distributions like Fedora or CentOS, you can follow below method. My machine’s actual RAM size is 4GB out of which I am going to use 1024MB for ramdisk.
NOTE: You can also use below method How to Create RAMDISK on Ubuntu.
# mkdir -p /media/ramdisk
# mount -t tmpfs -o size=1024M tmpfs /media/ramdisk/