This is how I create RAM disk manually on Linux Debian Jessie:
mount -o size=1G -t tmpfs none /mnt/tmpfs
My question is, how do I make this automatic at each computer startup?
You don't need a script for that: there's a system facility to mount a filesystem at boot time. Add it to the file
/etc/fstab. Open this file in your favorite text editor and add a line like this:
none /mnt/tmpfs tmpfs size=1G
Make sure not to accidentally modify other lines.
Note that there's already a tmpfs filesystem¹ mounted at
/run. Debian doesn't make
/tmp tmpfs by default, but you can make it so by editing
/etc/default/tmpfs and changing the
RAMTMP line to
¹ This isn't a RAM disk: it doesn't reserve memory, only the space used for files takes up memory, and its pages can be swapped out just like application data.