Operating System will work based on files, there may be the executable files or configuration files. Here in this post you can find the most important directories of Unix OS.
The below list shows you the main UNIX Directories and the file type of each directory.
/usr. This is the main location of binaries for both user and administrative purposes.
/usr/bin. This directory contains user binaries.
/usr/local. This directory is used for locally installed software that is typically separate from the OS. The binaries are typically stored in /usr/local/bin.
/usr/sbin. Binaries that are required for system administration purposes are stored here. This directory is not typically on a normal user’s path. On some versions of UNIX, some of the system binaries are stored in /sbin.
/usr/ucb. For non-BSD systems, this directory contains binaries that originated in BSD.
/usr/include. User header files are stored here. Header files used by the kernel are stored in /usr/include/sys.
/usr/share. This directory contains architecture-dependent files including ASCII help files. The UNIX manual pages are typically stored in /usr/share/man.
/usr/src. The UNIX kernel source code was once held in this directory although this hasn’t been the case for a long time, Linux excepted.
/usr/lib. Dynamic and shared libraries are stored here.
/bin. Has been a symlink to /usr/bin for quite some time.
/dev. All of the accessible device files are stored here.
/etc. Holds configuration files and binaries which may need to be run before other filesystems are mounted. This includes many start-up scripts and configuration files which are needed when the system bootstraps.
/var/preserve. This directory is used by the vi and ex editors for storing backup files.
/var/tmp. Used for user temporary files.
/var. System log files are stored here. Many of the log files are stored in/var/log.
/var/adm. UNIX accounting files and system log-in files are stored here.
/var/spool. This directory is used for UNIX commands that provide spooling services such as uucp, printing, and the cron command.
/tmp. This directory is used for temporary files. Files residing in this directory will not necessarily be there after the next reboot.
/home. User home directories are typically stored here. This may be /usr/home on some systems. Older versions of UNIX and BSD often store user home directories under /u.
/opt. Used for optional packages and binaries. Third-party software vendors store their packages in this directory.