3.4 Directory Structure

The FreeBSD directory hierarchy is fundamental to obtaining an overall understanding of the system. The most important concept to grasp is that of the root directory, “/”. This directory is the first one mounted at boot time and it contains the base system necessary to prepare the operating system for multi-user operation. The root directory also contains mount points for other file systems that are mounted during the transition to multi-user operation.

A mount point is a directory where additional file systems can be grafted onto a parent file system (usually the root file system). This is further described in Section 3.5. Standard mount points include /usr, /var, /tmp, /mnt, and /cdrom. These directories are usually referenced to entries in the file /etc/fstab. /etc/fstab is a table of various file systems and mount points for reference by the system. Most of the file systems in /etc/fstab are mounted automatically at boot time from the script rc(8) unless they contain the noauto option. Details can be found in Section 3.6.1.

A complete description of the file system hierarchy is available in hier(7). For now, a brief overview of the most common directories will suffice.

Directory Description
/ Root directory of the file system.
/bin/ User utilities fundamental to both single-user and multi-user environments.
/boot/ Programs and configuration files used during operating system bootstrap.
/boot/defaults/ Default bootstrapping configuration files; see loader.conf(5).
/dev/ Device nodes; see intro(4).
/etc/ System configuration files and scripts.
/etc/defaults/ Default system configuration files; see rc(8).
/etc/mail/ Configuration files for mail transport agents such as sendmail(8).
/etc/namedb/ named configuration files; see named(8).
/etc/periodic/ Scripts that are run daily, weekly, and monthly, via cron(8); see periodic(8).
/etc/ppp/ ppp configuration files; see ppp(8).
/mnt/ Empty directory commonly used by system administrators as a temporary mount point.
/proc/ Process file system; see procfs(5), mount_procfs(8).
/rescue/ Statically linked programs for emergency recovery; see rescue(8).
/root/ Home directory for the root account.
/sbin/ System programs and administration utilities fundamental to both single-user and multi-user environments.
/tmp/ Temporary files. The contents of /tmp are usually NOT preserved across a system reboot. A memory-based file system is often mounted at /tmp. This can be automated using the tmpmfs-related variables of rc.conf(5) (or with an entry in /etc/fstab; see mdmfs(8)).
/usr/ The majority of user utilities and applications.
/usr/bin/ Common utilities, programming tools, and applications.
/usr/include/ Standard C include files.
/usr/lib/ Archive libraries.
/usr/libdata/ Miscellaneous utility data files.
/usr/libexec/ System daemons & system utilities (executed by other programs).
/usr/local/ Local executables, libraries, etc. Also used as the default destination for the FreeBSD ports framework. Within /usr/local, the general layout sketched out by hier(7) for /usr should be used. Exceptions are the man directory, which is directly under /usr/local rather than under /usr/local/share, and the ports documentation is in share/doc/port.
/usr/obj/ Architecture-specific target tree produced by building the /usr/src tree.
/usr/ports The FreeBSD Ports Collection (optional).
/usr/sbin/ System daemons & system utilities (executed by users).
/usr/share/ Architecture-independent files.
/usr/src/ BSD and/or local source files.
/usr/X11R6/ X11R6 distribution executables, libraries, etc (optional).
/var/ Multi-purpose log, temporary, transient, and spool files. A memory-based file system is sometimes mounted at /var. This can be automated using the varmfs-related variables of rc.conf(5) (or with an entry in /etc/fstab; see mdmfs(8)).
/var/log/ Miscellaneous system log files.
/var/mail/ User mailbox files.
/var/spool/ Miscellaneous printer and mail system spooling directories.
/var/tmp/ Temporary files. The files are usually preserved across a system reboot, unless /var is a memory-based file system.
/var/yp NIS maps.

This, and other documents, can be downloaded from ftp://ftp.FreeBSD.org/pub/FreeBSD/doc/.

For questions about FreeBSD, read the documentation before contacting <questions@FreeBSD.org>.
For questions about this documentation, e-mail <doc@FreeBSD.org>.