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／etc directory

Created on · Last Modified on

/etc directory contains host-specific system-wide configuration files

Origin of Name

There has been controversy over the meaning of the name itself. In early versions of the UNIX Implementation Document from Bell labs, /etc is referred to as the etcetera directory, as this directory historically held everything that did not belong elsewhere (however, the FHS restricts /etc to static configuration files and may not contain binaries). Since the publication of early documentation, the directory name has been re-explained in various ways. Recent interpretations include backronyms such as “Editable Text Configuration” or “Extended Tool Chest”.

Subdirectories

sub directory

description

shadow
  • /etc/passwd - the user database, with fields giving the username, real name, home directory, and other information about each user
  • /etc/shadow - is an encrypted file the holds user passwords

group
  • similar to /etc/passwd, but describes groups instead of users

shells

/etc/login.defs
  • configuration file for the login command

/etc/profile
/etc/bashrc
/etc/csh.cshrc
  • shell profiles executed at login or startup time by the UNIX shells
  • allows the system administrator to set global defaults for all users
  • users can also create individual copies of these in their home directory to personalize their environment

fstab
  • contains 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

mtab
  • list of currently mounted filesystems. Initially set up by the bootup scripts, and updated automatically by the mount command

/etc/inittab
  • configuration file for init

/etc/crontab
  • list of running crons

/etc/motd
  • 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

sudoers
*
  • /etc/sudoers - is a file administrators use to allocate system rights to system users
  • /etc/sudoers.d - is a directory containing all the dropin files

/etc/opt
  • contains configuration files for add-on packages that are stored in /opt

/etc/sgml
  • contains configuration files, such as catalogs, for software that processes SGML

/etc/X11

/etc/xml
  • contains configuration files, such as catalogs, for software that processes XML

alternatives
  • used in keeping track of the alternatives currently in use, by a tool called update-alternatives