## 4.16. Important Directories

You already know about /home, where user files are stored. As a system administrator and programmer, several other directories will be important to you. Here are a few, along with their contents:

/bin

  The most essential Unix commands, such as `ls`.

/usr/bin

  Other commands. The distinction between /bin and /usr/bin is arbitrary; it was a convenient way to split up commands on early Unix systems that had small disks.

/usr/sbin

  Commands used by the superuser for system administration.

/boot

  Location where the kernel and other files used during booting are sometimes stored.

/etc

  Files used by subsystems such as networking, NFS, and mail. Typically, these contain tables of network services, disks to mount, and so on.

/var

  Administrative files, such as log files, used by various utilities.

/var/spool

  Temporary storage for files being printed, sent by UUCP, and so on.

/usr/lib

  Standard libraries, such as libc.a. When you link a program, the linker always searches here for the libraries specified in -l options.

/usr/lib/X11

  The X Window System distribution. Contains the libraries used by X clients, as well as fonts, sample resources files, and other important parts of the X package. This directory is usually a symbolic link to /usr/X11R6/lib/X11.

/usr/include

  Standard location of include files used in C programs, such as <stdio.h>.

/usr/src

  Location of sources to programs built on the system.

/usr/local

  Programs and data files that have been added locally by the system administrator.

/etc/skel

  Sample startup files you can place in home directories for new users.

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