The /etc directory
Keywords: sag

Next: The /dev directory Up: The root filesystem Previous: The root filesystem

## The `/etc` directory

The `/etc` directory contains a lot of files. Some of them are described below. For others, you should determine which program they belong to and read the manual page for that program. Many networking configuration files are in `/etc` as well, and are described in the Networking Administrators' Guide.

`/etc/rc` or `/etc/rc.d` or `/etc/rc?.d`
  Scripts or directories of scripts to run at startup or when changing the run level. See the chapter on `init` for further information.

`/etc/passwd`
  The user database, with fields giving the username, real name, home directory, encrypted password, and other information about each user. The format is documented in the passwd manual page.

`/etc/fdprm`
  Floppy disk parameter table. Describes what different floppy disk formats look like. Used by `setfdprm` . See the setfdprm manual page for more information.

`/etc/fstab`
  Lists the filesystems mounted automatically at startup by the `mount -a` command (in `/etc/rc` or equivalent startup file). Under Linux, also contains information about swap areas used automatically by `swapon -a`. See section 4.8.5 and the mount manual page for more information.

`/etc/group`
  Similar to `/etc/passwd` , but describes groups instead of users. See the group manual page for more information.

`/etc/inittab`
  Configuration file for `init` .

`/etc/issue`
  Output by `getty` before the login prompt. Usually contains a short description or welcoming message to the system. The contents are up to the system administrator.

`/etc/magic`
  The configuration file for `file` . Contains the descriptions of various file formats based on which `file` guesses the type of the file. See the magic and file manual pages for more information.

`/etc/motd`
  The message of the day, automatically output after a successful login. Contents are up to the system administrator. Often used for getting information to every user, such as warnings about planned downtimes.

`/etc/mtab`
  List of currently mounted filesystems. Initially set up by the scripts, and updated automatically by the `mount` command. Used when a list of mounted filesystems is needed, e.g., by the `df` command.

`/etc/shadow`
  Shadow password file on systems with shadow password software installed. Shadow passwords move the encrypted password from `/etc/passwd` into `/etc/shadow` ; the latter is not readable by anyone except `root`. This makes it harder to crack passwords.

`/etc/login.defs`
  Configuration file for the `login` command.

`/etc/printcap`
  Like `/etc/termcap` , but intended for printers. Different syntax.

`/etc/profile` , `/etc/csh.login` , `/etc/csh.cshrc`
  Files executed at login or startup time by the Bourne or C shells. These allow the system administrator to set global defaults for all users. See the manual pages for the respective shells.

`/etc/securetty`
  Identifies secure terminals, i.e., the terminals from which `root` is allowed to log in. Typically only the virtual consoles are listed, so that it becomes impossible (or at least harder) to gain superuser privileges by breaking into a system over a modem or a network.

`/etc/shells`
  Lists trusted shells. The `chsh` command allows users to change their login shell only to shells listed in this file. `ftpd` , the server process that provides FTP services for a machine, will check that the user's shell is listed in `/etc/shells` and will not let people log in unles the shell is listed there.

`/etc/termcap`
  The terminal capability database. Describes by what ``escape sequences'' various terminals can be controlled. Programs are written so that instead of directly outputting an escape sequence that only works on a particular brand of terminal, they look up the correct sequence to do whatever it is they want to do in `/etc/termcap` . As a result most programs work with most kinds of terminals. See the termcap , curs_termcap , and terminfo manual pages for more information.

Next: The /dev directory Up: The root filesystem Previous: The root filesystem