3.2.4. The most important configuration files
As we mentioned before, most configuration files are stored in the /etc directory. Content can be viewed using the cat command, which sends text files to the standard output (usually your monitor). The syntax is straight forward:
cat file1 file2 ... fileN
In this section we try to give an overview of the most common configuration files. This is certainly not a complete list. Adding extra packages may also add extra configuration files in /etc . When reading the configuration files, you will find that they are usually quite well commented and self-explanatory. Some files also have man pages which contain extra documentation, such as man group .
Table 3-3. Most common configuration files
File
Information/service
aliases
Mail aliases file for use with the Sendmail and Postfix mail server. Running a mail server on each and every system has long been common use in the UNIX world, and almost every Linux distribution still comes with a Sendmail package. In this file local user names are matched with real names as they occur in E-mail addresses, or with other local addresses.
apache
Config files for the Apache web server.
bashrc
The system-wide configuration file for the Bourne Again SHell. Defines functions and aliases for all users. Other shells may have their own system-wide config files, like cshrc
.
crontab
and the cron.*
directories
Configuration of tasks that need to be executed periodically - backups, updates of the system databases, cleaning of the system, rotating logs etc.
default
Default options for certain commands, such as useradd
.
filesystems
Known file systems: ext3, vfat, iso9660 etc.
fstab
Lists partitions and their mount points
.
ftp*
Configuration of the ftp-server: who can connect, what parts of the system are accessible etc.
group
Configuration file for user groups. Use the shadow utilities groupadd
, groupmod
and groupdel
to edit this file. Edit manually only if you really know what you are doing.
hosts
A list of machines that can be contacted using the network, but without the need for a domain name service. This has nothing to do with the system's network configuration, which is done in /etc/sysconfig
.
inittab
Information for booting: mode, number of text consoles etc.
issue
Information about the distribution (release version and/or kernel info).
ld.so.conf
Locations of library files.
lilo.conf
, silo.conf
, aboot.conf
etc.
Boot information for the LInux LOader, the system for booting that is now gradually being replaced with GRUB.
logrotate.*
Rotation of the logs, a system preventing the collection of huge amounts of log files.
mail
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