As you're using Unix, you'll undoubtedly encounter files that look important or directories that look interesting, but it's often hard to know what files belong to which programs, and even harder to figure out what some directories are for. Therefore, we're trying to help out a little with the information in this appendix.
Table B.1. Key Files in Your Unix Environment
Includes address(es) to forward mail to or redirects mail to a vacation program or to procmail.
Includes records of read, unread, and subscribed newsgroups for use by news readers.
Includes configuration information for procmail.
Includes configuration information for pine.
Includes configuration information for mutt.
Contains your signature, which is appended to your messages by email programs and news readers.
Systemwide bash resource file shared by all bash users.
Systemwide csh resource file.
System group records.
Systemwide configuration files for ksh users.
System passwords and user records.
Systemwide configuration file used by bash and ksh.
Original configuration files placed into the home directory of new users.
Primary personal configuration file for bash users.
Resource file for csh users.
Configuration file for ksh users.
Configuration file for csh users in a login shell.
Primary configuration file for ksh users; used by bash if .bash_profile isn't available.
Configuration file for zsh users in a login shell.
Resource file for zsh users.
Configuration file for zsh users.
Environment file for zsh users.
Mail directory customarily used by pine.
Mail directory customarily used by system mailer and mutt.
Includes configuration information used by make to compile and install new software.
Includes important information, usually distributed with a new program or script, about installation or usage.
Table B.2. Common Unix Directories and Their Contents
Essential programs and commands for use by all users.
Files that the system boot loader uses.
Devices (CD-ROM, serial ports, etc.) and special files.
System configuration files and global settings.
Template configuration files for individual users.
Configuration files and information for the X Window System.
Home directories for users.
Essential shared libraries and kernel modules.
Mount point for temporarily mounted file systems.
Directory for add-on application software packages.
Location of kernel and process information (virtual file system).
Home directory for the root user/system administrator.
Essential programs and commands for system boot.
Commands and programs that are less essential for basic Unix system functionality than those in /bin but were installed with the system.
Standard include files and header files for C programs.
Libraries for programming and for installed packages.
Most files and data that were developed or customized on the system.
Locally developed or installed programs.
Manual (help) pages for local programs.
Source code for locally developed or installed programs.
Additional nonessential standard system binaries.
Shared (system-independent) data files.
Manual (help) pages for standard programs.
Miscellaneous shared system-independent data.
Source code for standard programs.
X Window System, Version 11 Release 6.
X Window System, Version 11 Release 5, on x86 platforms.
Changeable data, including system logs, temporary data from programs, and user mail storage.
Accounting logs, if applicable.
Administrative log files and directories.
Application-specific cache data.
Locally generated fonts.
Formatted versions of manual pages.
Information stored from system crashes, if applicable.
Variable game data.
Lock files created by various programs.
Log files and directories.
User mailbox files.
Run-time variable files.
General application spool data.
Contains cron and at job schedules.
Line-printer daemon print queues.
Contains incoming mail for users.
Variable state information for the system.
Editor backup files and state information.
Miscellaneous variable data.
Temporary files that the system keeps through reboots.
Database files that the Network Information Service (NIS) uses.