What are Linux configuration files?

Linux configuration files enable the Kernel to know about users, their login state, and manage file permissions and user groups. Most of the configuration files in Linux are usually under the /etc folder.

The configuration files are static and cannot be executable. They are used to control the operation of various Linux programs.

Broadly speaking, Linux configuration files can be of the following types.

Access files

Access files tell the network domain how to look up host names. Access files include:

• /etc/hosts.config
• /etc/hosts
• /etc/hosts.allow
• /etc/hosts.deny

Booting and login/logout

These files contain configuration information for booting up the system.

• /etc/issue & /etc/issue.net

• /etc/rc.d/rc

• /etc/rc.d/rc.sysinit

• /etc/rc.d/rc/rc X.d

File system

Linux provides /proc, a virtual file system that can be used to display various system data structures and parameters.

Many programs access this file system to gain statistical information about the system, such as the devices mounted on the system, the memory usage, etc.

• /etc/mtab
• /etc/fstab
• /etc/mtools.conf

System administration

This group of files contains information about the users and user groups, as well as the file permissions and credentials of all users. These files include the following configuration files:

• /etc/group
• /etc/nologin
• etc/passwd
• /etc/rpmrc
• /etc/securetty
• /etc/usertty
• /etc/shadow

System commands

System commands are meant to be used exclusively by the system. Programs like login or bash are all system commands. These are important files containing information about the system commands and include the following files.

• /etc/lilo.conf
• /etc/logrotate.conf
• /etc/identd.conf
• /etc/ld.so.conf
• /etc/inittab
• /etc/termcap

Daemons

Daemons are programs that run in the background without user interference. These are often related to networking stacks, where they wait for connections to arrive so that they can provide services through them.

• /etc/syslogd.conf
• ​*/etc/httpd.conf*
• ​*/etc/conf.modules*