Use tmpfs in Ubuntu to speed up

Why? Sometime, you will use USB stick to boot up to another testing Ubuntu distribution, but the USB stick as main disk is really slow. So, I choose to use Linux tmpfs to avoid un-necessary access.

/etc/fstab
tmpfs           /tmp            tmpfs   defaults,noatime,mode=1777      0       0

tmpfs           /var/spool      tmpfs   defaults,noatime,mode=1777      0       0
tmpfs           /var/tmp        tmpfs   defaults,noatime,mode=1777      0       0