Debian Directory Structure

A description of the hierarchy specified in the FHS

/bin/

Essential command executable (binaries) for all users (e.g., cat, ls, cp) 
(especially files required to boot or rescue the system)

/boot/

Boot loader, kernels and initrd files

/dev/

devices files (e.g., :/dev/null)

/etc/

Host-specific system-wide configuration files (from et cetera)

/home/

Users' home directories

/lib/

Libraries essential for the binaries in /bin/ and /sbin/ 
(library required to boot or rescue the system)

/lost+found/

Some files and fragment that were "recovered" during the previous fsck (Not part of FHS)

/mnt/

Temporarily mounted filesystems

/media/

Mount points for removable media such as CD-ROMs (appeared in FHS-2.3)

/opt/

Add-on application software packages 
Pre-compiled, non ".deb" binary distribution (tar'ed..) goes here.

/opt/bin/ : Same as for top-level hierarchy

/opt/include/ : Same as for top-level hierarchy

/opt/lib/ : Same as for top-level hierarchy

/opt/sbin/ : Same as for top-level hierarchy

/opt/share/ : Same as for top-level hierarchy

/proc/

Virtual filesystem documenting kernel and process status, mostly text files (e.g., uptime, network)

/root/

Home directory for the root user

/sbin/

System administrative binaries (e.g., init, route, ifup) (system binaries) 
(files required to boot or rescue the system)

/tmp/

Temporary files

/selinux/

SE-Linux runtime settings (Not part of FHS).

/srv/

Site-specific data which is served by the system (Not part of FHS).

/sys/

The filesystem for exporting kernel objects.
(many /proc/* files should have been here...)

/usr/

Secondary hierarchy for shareable, read-only data (formerly from UNIX source repository, now from UNIX system resources) 
(files that are not-required to boot or rescue the system)

/usr/bin/ : Same as for top-level hierarchy

/usr/include/ : Standard include files

/usr/lib/ : Same as for top-level hierarchy

/usr/sbin/ : Same as for top-level hierarchy

/usr/share/ : Architecture-independent (shared) data

/usr/src/ : Source code (to build debian packages. see also /usr/local/src/)

/usr/X11R6/ : X Window System, Version 11 Release 6

/usr/local/ : Tertiary hierarchy for local data installed by the system administrator

• /usr/local/bin : locally compiled binaries, local shell script, etc.

• /usr/local/src : Source code (place where to extract and build non debian'ized stuffs)

/var/

Variable data, such as logs, databases, websites, and temporary spool (e-mail..) files