Different distributions have different directory structures.
/bin – essential UNIX commands such as ls, etc. Should contain all binaries needed to boot the system or run it in single-user mode
/boot – files used during booting and possibly the kernel itself are stored here
/dev – contains device files for various devices on system
/etc – files used by subsystems such as networking, NFS, and mail. Includes tables of disks to mount, processes to run on startup, etc.
/etc/profile.d – contains scripts that are run by /etc/profile upon login.
/etc/rc.d – contains a number of shell scripts that are run on bootup at different run levels. There is also typically an rc.inet1 script to set up networking (in Slackwar), an rc.modules script to load modular device drivers, and an rc.local script that can be edited to run commands desired by the administrator, along the lines of autoexec.bat in DOS.
/etc/rc.d/init.d – contains most of the initialization scripts themselves on an rpm-based system.
/etc/rc.d/rc*.d – where “*'' is a number corresponding to the default run level. Contains files for services to be started and stopped at that run level. On rpm-based systems, these files are symbolic links to the initialization scripts themselves, which are in /etc/rc.d/init.d.
/etc/skel – directory containing several example or skeleton initialization shells. Often contains subdirectories and files used to populate a new user's home directory.
/etc/X11 – configuration files for the X Window system
/home – home directories of individual users
/lib – standard shared library files
/lib/modules – modular device driver files, most with .o extensions
/mnt – typical mount point for many user-mountable devices such as floppy drives, cd-rom readers, etc. Each device is mounted on a subdirectory of /mnt.
/proc – virtual file system that provides a number of system statistics
/root – home directory for root
/sbin – location of binaries used for system administration, configuration, and monitoring
/tmp – directory specifically designed for programs and users to store temporary files.
/usr – directory containing a number of subdirectory with programs, libraries, documentation, etc.
/usr/bin – contains most user commands. Should not contain binaries necessary for booting the system, which go in /bin. The /bin directory is generally located on the same disk partition as /, which is mounted in read-only mode during the boot process. Other filesystems are only mounted at a later stage during startup, so putting binaries essential for boot here is not a good idea.
/usr/bin/X11 – most often a symbolic link to /usr/X11R6/bin, which contains executable binaries related to the X Window system
/usr/doc – location of miscellaneous documentation, and the main location of program documentation files under Slackware
/usr/include – standard location of include files used in C programs such as stdio.h
/usr/info – primary location of the GNU info system files
/usr/lib – standard library files such as libc.a. Searched by the linker when programs are compiled.
/usr/lib/X11 – X Window system distribution
/usr/local/bin – yet another place to look for comon executables
/usr/man – location of manual page files
/usr/sbin – other commands used by superuser for system administration
/usr/share – contains subdirectories where many installed programs have configuration, setup and auxiliary files
/usr/share/doc – location of program documentation files under Mandrake and Red Hat
/usr/src – location of source programs used to build system. Source code for programs of all types are often unpacked in this directory.
/usr/src/linux – often a symbolic link to a subdirectory whose name corresponds to the exact version of the Linux kernel that is running. Contains the kernel sources.
/var – administrative files such as log files, used by various utilities
/var/log/packages – contains files, each of which has detailed information on an installed package in Slackware. The same file can also be found at /var/adm/packages, since the adm subdirectory is a symbolic link to log. Each package file contains a short description plus a list of all installed files.
/var/log/scripts – package installation scripts in Slackware are stored here. You can inspect these scripts to see what special features are included in individual packages.
/var/spool – temporary storage for files being printed, mail that has not yet been picked up, etc.