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<A NAME="730"> </A><H2><A NAME="SECTION00421000000000000000">The <tt>/etc</tt> directory</A></H2>
<P>
The <tt>/etc</tt><A NAME="732"> </A> 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 <tt>/etc</tt><A NAME="734"> </A> as well,
and are described in the Networking Administrators' Guide.
<DL ><DT><STRONG><tt>/etc/rc</tt><A NAME="736"> </A> or <tt>/etc/rc.d</tt><A NAME="738"> </A> or <tt>/etc/rc?.d</tt><A NAME="740"> </A></STRONG>
<DD>
Scripts or directories of scripts to run at startup or when
changing the run level.
See the chapter on <tt>init</tt><A NAME="742"> </A> for further information.
<P>
<DT><STRONG><tt>/etc/passwd</tt><A NAME="744"> </A></STRONG>
<DD>
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 <em>passwd</em><A NAME="746"> </A>
manual page.
<P>
<DT><STRONG><tt>/etc/fdprm</tt><A NAME="748"> </A></STRONG>
<DD>
Floppy disk parameter table. Describes what different floppy
disk formats look like. Used by <tt>setfdprm</tt><A NAME="750"> </A>. See
the <em>setfdprm</em><A NAME="752"> </A> manual page for more information.
<P>
<DT><STRONG><tt>/etc/fstab</tt><A NAME="754"> </A></STRONG>
<DD>
Lists the filesystems mounted automatically at startup
by the <tt>mount -a</tt> command (in <tt>/etc/rc</tt><A NAME="756"> </A> or equivalent
startup file). Under Linux, also contains information about swap
areas used automatically by <tt>swapon -a</tt>.
See section <A HREF="node46.html#subsecmount">4.8.5</A> and the
<em>mount</em><A NAME="758"> </A> manual page for more information.
<P>
<DT><STRONG><tt>/etc/group</tt><A NAME="760"> </A></STRONG>
<DD>
Similar to <tt>/etc/passwd</tt><A NAME="762"> </A>, but describes
groups instead of users. See the <em>group</em><A NAME="764"> </A> manual page for
more information.
<P>
<DT><STRONG><tt>/etc/inittab</tt><A NAME="766"> </A></STRONG>
<DD>
Configuration file for <tt>init</tt><A NAME="768"> </A>.
<P>
<DT><STRONG><tt>/etc/issue</tt><A NAME="770"> </A></STRONG>
<DD>
Output by <tt>getty</tt><A NAME="772"> </A> before the login prompt. Usually contains
a short description or welcoming message to the system. The
contents are up to the system administrator.
<P>
<DT><STRONG><tt>/etc/magic</tt><A NAME="774"> </A></STRONG>
<DD>
The configuration file for <tt>file</tt><A NAME="776"> </A>. Contains
the descriptions of various file formats based on which
<tt>file</tt><A NAME="778"> </A> guesses the type of the file. See the <em>magic</em><A NAME="780"> </A>
and <em>file</em><A NAME="782"> </A> manual pages for more information.
<P>
<DT><STRONG><tt>/etc/motd</tt><A NAME="784"> </A></STRONG>
<DD>
The <b>message of the day</b>, 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.
<P>
<DT><STRONG><tt>/etc/mtab</tt><A NAME="787"> </A></STRONG>
<DD>
List of currently mounted filesystems. Initially set up by
the scripts, and updated automatically by the <tt>mount</tt><A NAME="789"> </A> command.
Used when a list of mounted filesystems is needed, e.g., by
the <tt>df</tt><A NAME="791"> </A> command.
<P>
<DT><STRONG><tt>/etc/shadow</tt><A NAME="793"> </A></STRONG>
<DD>
Shadow password file on systems with shadow password software
installed. Shadow passwords move the encrypted password from
<tt>/etc/passwd</tt><A NAME="795"> </A> into <tt>/etc/shadow</tt><A NAME="797"> </A>; the latter is not
readable by anyone except <tt>root</tt>. This makes it harder
to crack passwords.
<P>
<DT><STRONG><tt>/etc/login.defs</tt><A NAME="799"> </A></STRONG>
<DD>
Configuration file for the <tt>login</tt><A NAME="801"> </A> command.
<P>
<DT><STRONG><tt>/etc/printcap</tt><A NAME="803"> </A></STRONG>
<DD>
Like <tt>/etc/termcap</tt><A NAME="805"> </A>, but intended for printers. Different
syntax.
<P>
<DT><STRONG><tt>/etc/profile</tt><A NAME="807"> </A>, <tt>/etc/csh.login</tt><A NAME="809"> </A>, <tt>/etc/csh.cshrc</tt><A NAME="811"> </A></STRONG>
<DD>
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.
<P>
<DT><STRONG><tt>/etc/securetty</tt><A NAME="813"> </A></STRONG>
<DD>
Identifies secure terminals, i.e., the terminals from which
<tt>root</tt> 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.
<P>
<DT><STRONG><tt>/etc/shells</tt><A NAME="815"> </A></STRONG>
<DD>
Lists trusted shells. The <tt>chsh</tt><A NAME="817"> </A> command allows users
to change their login shell only to shells listed in this
file. <tt>ftpd</tt><A NAME="819"> </A>, the server process that provides FTP
services for a machine, will check that the user's shell is
listed in <tt>/etc/shells</tt><A NAME="821"> </A> and will not let people log in
unles the shell is listed there.
<P>
<DT><STRONG><tt>/etc/termcap</tt><A NAME="823"> </A></STRONG>
<DD>
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 <tt>/etc/termcap</tt><A NAME="825"> </A>. As a result most programs
work with most kinds of terminals. See the
<em>termcap</em><A NAME="827"> </A>, <em>curs_termcap</em><A NAME="829"> </A>, and <em>terminfo</em><A NAME="831"> </A>
manual pages for more information.
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<P><ADDRESS>
<I>Lars Wirzenius <BR>
Sat Nov 15 02:32:11 EET 1997</I>
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