Title : Use ramdisk on /tmp on OpenBSD Author: Solène Date : 08 May 2018 Tags : openbsd66 openbsd 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.