On my new OpenBSD servers, I decided to use memory filesystem for /tmp. After looking at old servers usage, I decided that 64M of memory space would be enough.
# grep mfs /etc/fstab swap /tmp mfs rw,nodev,nosuid,-s=64m 0 0
And that seemed well sized. Until I ran syspatch(8) and got a whole bunch of errors:
# doas /usr/sbin/syspatch Get/Verify syspatch65-001_rip6cks... 100% Installing patch 001_rip6cksum Get/Verify syspatch65-002_srtp.tgz 100% Installing patch 002_srtp Get/Verify syspatch65-003_mds.tgz 100% Installing patch 003_mds /tmp: write failed, file system is full tar: Failed write to file usr/share/relink/kernel/GENERIC.MP/sys_pipe.o: No space left on device tar: Failed write to file usr/share/relink/kernel/GENERIC.MP/sys_process.o: No space left on device (...)tar: Unable to create usr/share/relink/kernel/GENERIC.MP/xen.o: No space left on device tar: Failed write to file var/syspatch/65-003_mds/003_mds.patch.sig: No space left on device Relinking to create unique kernel... done; reboot to load the new kernel Errata can be reviewed under /var/syspatch
After trying a few values, I finally went for 256M. Free space didn’t go under 100M.
# grep mfs /etc/fstab swap /tmp mfs rw,nodev,nosuid,-s=256m 0 0