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| | 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 the section called Mounting and unmounting in Chapter 4 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 bootup 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.
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