FHS

ファイルシステム階層標準（Filesystem Hierarchy Standard）。一般的にLinuxシステムは以下のようなディレクトリ構造になっている。下記はDebian11の「$man hier」の内容。

ディレクトリ	説明
/	This is the root directory. This is where the whole tree starts.
/bin -> usr/bin	This directory contains executable programs which are needed in single user mode and to bring the system up or repair it.
/usr/bin	This is the primary directory for executable programs. 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.
/boot	Contains static files for the boot loader. This directory holds only the files which are needed during the boot process. The map installer and configuration files should go to /sbin and /etc. The operating system kernel (initrd for example) must be located in either / or /boot.
/dev	Special or device files, which refer to physical devices. See mknod(1).
/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 (optional).
/lost+found	This directory contains items lost in the filesystem. These items are usually chunks of files mangled as a consequence of a faulty disk or a system crash.

/etc

ディレクトリ	説明
/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/opt	Host-specific configuration files for add-on applications installed in /opt.
/etc/skel	When a new user account is created, files from this directory are usually copied into the user's home directory.
/etc/sgml	This directory contains the configuration files for SGML (optional).
/etc/X11	Configuration files for the X11 window system (optional).
/etc/xml	This directory contains the configuration files for XML (optional).

/lib

ディレクトリ	説明
/lib	This directory should hold those shared libraries that are necessary to boot the system and to run the commands in the root filesystem.
/lib<qual>	These directories are variants of /lib on system which support more than one binary format requiring separate libraries (optional).
/lib/modules	Loadable kernel modules (optional).

/media

ディレクトリ	説明
/media	This directory contains mount points for removable media such as CD and DVD disks or USB sticks. On systems where more than one device exists for mounting a certain type of media, mount directories can be created by appending a digit to the name of those available above starting with '0', but the unqualified name must also exist.
/media/floppy[1-9]	Floppy drive (optional).
/media/cdron[1-9]	CD-ROM drive (optional).
/media/cdrecorder	CD writer (optional).
/media/zip[1-9]	Zip drive (optional).
/meida/usb[1-9]	USB drive (optional).

/usr

ディレクトリ	説明
/usr	This directory is usually mounted from a separate partition. It should hold only shareable, read-only data, so that it can be mounted by various machines running Linux.
/usr/X11R6	The X-Window system, version 11 release 6 (present in FHS 2.3, removed in FHS 3.0).
/usr/bin/mh	Commands for the MH mail handling system (optional).
/usr/bin/X11	is the traditional place to look for X11 executables; on Linux, it usually is a symbolic link to /usr/X11R6/bin.
/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/games	Binaries for games and educational programs (optional).
/usr/include	Include files for the C compiler.
/usr/include/bsd	BSD compatibility include files (optional).
/usr/include/X11	Include files for the C compiler and the X-Window 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.)
/usr/include/g++	Include files to use with the GNU C++ compiler.
/usr/lib	Object libraries, including dynamic libraries, plus some executables which usually are not invoked directly. More complicated programs may have whole subdirectories there.
/usr/libexec	Directory contains binaries for internal use only and they are not meant to be executed directly by users shell or scripts.
/usr/lib<qual>	These directories are variants of /usr/lib on system which support more than one binary format requiring separate libraries, except that the symbolic link /usr/lib<qual>/X11 is not required (optional).
/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 executables and include files for the GNU C compiler, gcc(1).
/usr/lib/groff	Files for the GNU groff document formatting system.
/usr/lib/uucp	Files for uucp(1).
/usr/local	This is where programs which are local to the site typically go.
/usr/local/bin	Binaries for programs local to the site.
/usr/local/doc	Local documentation.
/usr/local/etc	Configuration files associated with locally installed programs.
/usr/local/games	Binaries for locally installed games.
/usr/local/lib	Files associated with locally installed programs.
/usr/local/lib<qual>	These directories are variants of /usr/local/lib on system which support more than one binary format requiring separate libraries (optional).
/usr/local/include	Header files for the local C compiler.
/usr/local/info	Info pages associated with locally installed programs.
/usr/local/man	Man pages associated with locally installed programs.
/usr/local/sbin	Locally installed programs for system administration.
/usr/local/share	Local application data that can be shared among different architectures of the same OS.
/usr/local/src	Source code for locally installed software.
/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/color	Contains color management information, like International Color Consortium (ICC) Color profiles (optional).
/usr/share/dict	Contains the word lists used by spell checkers (optional).
/user/share/dict/words	List of English words (optional).
/usr/share/doc	Documentation about installed programs (optional).
/usr/share/games	Static data files for games in /usr/games (optional).
/user/share/info	Info pages go here (optional).
/usr/share/local	Locale information goes here (optional).
/usr/share/man	Manual pages go here in subdirectories according to the man page sections.
/user/share/misc	Miscellaneous data that can be shared among different architectures of the same OS.