Some useful configuration files and directories in linux

Below is useful configuration files and directories in Linux. Every DBA must be aware for daily operation.
File Name
/etc/passwd file is used to keep track of every registered user that has access to a system. File that contains the following information: Username. Encrypted password. User ID number (UID)
hosts file is an operating system file that maps hostnames to IP addresses.
The /etc/group file contains basic group attributes. This is an ASCII file that contains records for system groups. Each record appears on a single line and is the following format:


/etc/issue is a text file which contains a message or system identification to be printed before the login prompt
The /etc/resolv.conf is resolver configuration file for Linux and UNIX like operating systems.The file /etc/resolv.conf file contains information that is read by the resolver routines the first time they are invoked by a process.
The main configuration file for yum is /etc/yum.conf.The /etc/yum.conf configuration file contains exactly one [main] section. You can add many additional options under the [main] section heading in /etc/yum.conf.
if you install packages using the yum command, this log stores all related information, which can be useful in determining whether a package and all components were correctly installed.
The /etc/named.conf file is the configuration file for named.The /etc/named.conf file establishes the server as a master, slave, or cache-only name server.
The /etc/exports file controls which file systems are exported to remote hosts and specifies options.The file /etc/exports contains a table of local physical file systems on an NFS server that are accessible to NFS clients. The contents of the file are maintained by the server’s system administrator.
/etc/sudo.conf configuration file are allowed to use the sudo command and the command is executed in the user’s shell, not a root shell.
The snmp.conf file configures how the standard CUPS network backends (http, https, ipp, ipps, lpd, snmp, and socket) access printer information using SNMPv1 and is normally located in the /etc/cups directory.
The /etc/cups/cupsd.conf file contains configuration directives that control how the server functions.
The subscriptions.conf file defines the local event notification
subscriptions that are active.
/etc/cups/printers.conf file to store the list of available printers. This is the printer configuration file with entries for each print queue.
The client.conf file configures the CUPS client and is normally located in the /etc/cups or ~/.cups directory.
This shows you any files that might give a hint on the operating system version.
The Oracle inventory directory is used by the installer to keep track of all Oracle products installed on the computer. The inventory directory is stored in a file called oraInst.loc.
The NTP program is configured using either the /etc/ntp.conf
As the /etc/sysctl.conf file is used to override default kernel parameter values and therefore only contains a few of the possible parameters.
The bash history is a log file that contains all commands that the user executed on the Linux shell.
The ~/.bash_profile file is a configuration file for configuring user environments. The users can modify the default settings and add any extra configurations in it.
The ~/.bash_logout file contains instructions for the logout procedure.
The ~/.bash_login file contains specific settings that are executed when a user logs in to the system.
Stores all logs related to mail servers
Stores all Crond-related messages (cron jobs), such as when the cron daemon initiated a job, related failure messages, etc.
Stores Kernel logs and warning data. This log is valuable for troubleshooting custom kernels as well.
Messages relating to device drivers. The command dmesg can be used to view messages in this file.
Contains information all failed login attempts, which is useful for gaining insights on attempted security breaches, such as those attempting to hack login credentials as well as brute-force attacks.
A directory containing error_log and access_log files of the Apache httpd daemon
A repository of all information related to booting and any messages logged during startup.
/var/log/syslog or /var/log/messages
General messages, as well as system-related information. Essentially, this log stores all activity data across the global system.

List of useful configuration files and directories in linux : –

According to the Filesystem Hierarchy Standard, /opt is for “the installation of add-on application software packages
All binaries needed for the boot process and to run the system in single-user mode, including essential commands such as cd, ls, etc.
contains files used for system startup including the kernel
Contains device files for all hardware devices on the system
Files used by application subsystems such as mail, the Oracle database, etc.
Contains various service startup scripts
Holds application setup scripts run by /etc/profile upon login
Contains subdirectories which contain run level specific scripts
run level initialization scripts
Where ‘?’ is a number corresponding to the default run level. Contains symbolic links to scripts which are in /etc/rc.d/init.d. for services to be started and stopped at the indicated run level.
Holds example dot files used to populate a new user’s home directory.
Contains subdirectories and configuration files for the X Window system
User home directories
Some shared library directories, files, and links
The typical mount point for the user-mountable devices such as floppy drives and CDROM
Virtual file system that provides system statistics.  It doesn’t contain real files but provides an interface to runtime system information.
Commands used by the super user for system administrative functions
A standard repository for temporary files created by applications and users.
Directory contains subdirectories with source code, programs, libraries, documentation, etc.
Contains commands available to normal users
X Window system  binaries
Holds include files used in C programs
Contains shared directories for man files, info files, etc.
Library files searched by the linker when programs are compiled
Common executable application files local to this system
Commands used by the super user for system administrative functions
Administrative files such as log files, locks, spool files, and temporary files used by various utilities
This is the home directory of root user and should never be confused with ‘/‘
This directory is the only clean solution for early-runtime-dir problem.
Modern Linux distributions include a /sys directory as a virtual filesystem, which stores and allows modification of the devices connected to the system.

Hope you find it useful configuration files and directories in Linux to manage you daily jobs in Linux.

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