/

This is the root directory. This is where the whole tree starts.

/bin

This directory contains executable programs which are needed in single user mode and to bring the system up or repair it.

/boot

Contains static files for the boot loader. This directory only holds the files which are needed during the boot process.

/dev

Special or device files, which refer to physical devices.

/etc

Contains configuration files which are local to the machine. Some larger software packages, like X11, can have their own subdirectories below /etc. Site-wide configuration files may be placed here or in /usr/etc. Nevertheless, programs should always look for these files in /etc and you may have links for these files to /usr/etc.

/etc/skel

When a new user account is created, files from this directory are usually copied into the user's home directory.

/etc/X11

Configuration files for the X11 window system.

/home

On machines with home directories for users, these are usually beneath this directory, directly or not. The structure of this directory depends on local administration decisions.

/lib

This directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem.

/mnt

is a mount point for temporarily mounted filesystems

/proc

This is a mount point for the proc filesystem, which provides information about running processes and the kernel.

/sbin

Like /bin, this directory holds commands needed to boot the system, but which are usually not executed by normal users.

/tmp

This directory contains temporary files which may be deleted with no notice, such as by a regular job or at system boot up.

/usr

This directory is usually mounted from a separate partition. It should hold only sharable, read-only data, so that it can be mounted by various machines running Linux.

/usr/X11R6

The X-Window system.

/usr/bin

This is the primary directory for executable pro grams. Most programs executed by normal users which are not needed for booting or for repairing the system and which are not installed locally should be placed in this directory.

/usr/bin/X11

is the traditional place to look for X11 executable's; on Linux, it usually is a symbolic link to /usr/X11R6/bin.

/usr/dict

This directory holds files containing word lists for spell checkers.

/usr/doc

You may find documentation about the installed software packages in this directory.

/usr/etc

Site-wide configuration files to be shared between several machines may be stored in this directory. However, commands should always reference those files using the /etc directory. Links from files in /etc should point to the appropriate files in /usr/etc.

/usr/include

Include files for the C compiler.

/usr/include/X11

Include files for the C compiler and the X-Windows system. This is usually a symbolic link to /usr/X11R6/include/X11.

/usr/include/asm

Include files which declare some assembler functions. This used to be a symbolic link to /usr/src/linux/include/asm.

/usr/include/linux

This contains information which may change from system release to system release and used to be a symbolic link to /usr/src/linux/include/linux to get at operating system specific information.

(Note that one should have include files there that work correctly with the current libc and in user space. However, Linux kernel source is not designed to be used with user programs and does not know anything about the libc you are using. It is very likely that things will break if you let /usr/include/asm and /usr/include/linux point at a random kernel tree. Debian systems don't do this and use headers from a known good kernel version, provided in the libc*-dev package.)

Include files to use with the GNU C++ compiler.

/usr/lib

Object libraries, including dynamic libraries, plus some executable's which usually are not invoked directly. More complicated programs may have whole subdirectories there.

/usr/lib/X11

The usual place for data files associated with X programs, and configuration files for the X system itself. On Linux, it usually is a symbolic link to /usr/X11R6/lib/X11

/usr/lib/gcc-lib

contains executable's and include files for the GNU C compiler.

/usr/lib/groff

Files for the GNU groff document formatting system.

/usr/local

This is where programs which are local to the site typically go.

/usr/local/bin

Binaries for programs local to the site go there.

/usr/local/doc

Local documentation

/usr/local/etc

Configuration files associated with locally installed programs go there.

/usr/local/lib

Files associated with locally installed programs go there.

/usr/local/info

Info pages associated with locally installed pro grams go there.

/usr/local/man

Manpages associated with locally installed programs go there.

/usr/local/sbin

Locally installed programs for system administration.

/usr/local/src

Source code for locally installed software.

/usr/man

Manpages traditionally go in there, into their sub directories.

/usr/sbin

This directory contains program binaries for system administration which are not essential for the boot process, for mounting /usr, or for system repair.

/usr/share

This directory contains subdirectories with specific application data, that can be shared among different architectures of the same OS. Often one finds stuff here that used to live in /usr/doc or /usr/lib or /usr/man.

/usr/share/man

Manpages go in there, into their subdirectories.

/usr/src

Source files for different parts of the system, included with some packages for reference purposes. Don't work here with your own projects, as files below /usr should be read-only except when installing software

/usr/src/linux

This has always been the traditional place where kernel sources were unpacked. This was important on systems that /usr/include/linux was a symlink here. You should probably use another directory for building the kernel now.

/usr/tmp

Obsolete. This should be a link to /var/tmp. This link is present only for compatibility reasons and shouldn't be used.

/var

This directory contains files which may change in size, such as spool and log files.

/var/adm

This directory is superseded by /var/log and should be a symbolic link to /var/log.

/var/backups

This directory is used to save backup copies of important system files.

/var/lock

Lock files are placed in this directory. The naming convention for device lock files is LCK..<device> where <device> is the device's name in the filesystem. The format used is that of HDU UUCP lock files, i.e. lock files contain a PID as a 10-byte ASCII decimal number, followed by a newline character.

/var/log

Miscellaneous log files.

/var/preserve

This is where vi saves edit sessions so they can be restored later.

/var/run

Run-time variable files, like files holding process identifiers (PIDs) and logged user information (utmp). Files in this directory are usually cleared when the system boots.

/var/spool

Spooled (or queued) files for various programs.

/var/spool/at

Spooled jobs for at(1).

/var/spool/cron

Spooled jobs for cron

/var/spool/lpd

Spooled files for printing.

/var/spool/mail

Users' mailboxes.

/var/tmp

Like /tmp, this directory holds temporary files stored for an unspecified duration.