Title: Use ramdisk on /tmp on OpenBSD
       Author: Solène
       Date: 08 May 2018
       Tags: openbsd70 openbsd
       Description: 
       
       If you have enough memory on your system and that you can afford to
       use a few hundred megabytes to store temporary files, you may want to
       mount a mfs filesystem on /tmp. That will help saving your SSD drive,
       and if you use an old hard drive or a memory stick, that will reduce
       your disk load and improve performances. You may also want to mount a
       ramdisk on others mount points like ~/.cache/ or a database for some
       reason, but I will just explain how to achieve this for /tmp with is a
       very common use case.
       
       First, you may have heard about **tmpfs**, but it has been disabled in
       OpenBSD years ago because it wasn't stable enough and nobody fixed
       it. So, OpenBSD has a special filesystem named **mfs**, which is a FFS
       filesystem on a reserved memory space. When you mount a mfs
       filesystem, the size of the partition is reserved and can't be used
       for anything else (tmpfs, as the same on Linux, doesn't reserve the
       memory).
       
       Add the following line in /etc/fstab (following fstab(5)):
       
           swap /tmp mfs rw,nodev,nosuid,-s=300m 0 0
       
       The permissions of the mountpoint /tmp should be fixed **before**
       mounting it, meaning that the `/tmp` folder on `/` partition
       should be changed to 1777:
       
           # umount /tmp
           # chmod 1777 /tmp
           # mount /tmp
       
       This is required because **mount_mfs** inherits permissions from the
       mountpoint.