OpenBSD Filesystem Hierarchy

hier(7) explains the layout of OpenBSD's filesystems. Here is a brief overview:

Filesystem Hierarchy
/Root directory
/altroot/Alternate (backup) root
/bin/Fundamental utilities
/bsdKernel executable
/bsd.mpMultiprocessor kernel executable
/bsd.spSingle processor kernel executable
/bsd.rdInstallation kernel. Also useful for system maintenance
/etc/System conf files and scripts
/home/Home folder for user files
/mnt/Temporary mount point for new filesystems
/root/Home directory for superuser
/sbin/Essential system programs
/tmp/Temporary files deleted upon reboot
/usr/User utilities and applications
/usr/X11R6/X11 window files
/usr/local/Local executables and libraries including third-party software
/usr/src/BSD and local source
/usr/obj/Files built from source
/var/Log, spool, cronjob, web, mail, backup, and temporary files