October 21, 2021
Linux Command Line for beinngers

Linux (CentOS) Command Lines Beginners Should Know

Interacting with the Linux operating system, we can not only rely on the GUI (graphical user interfaces) but also often interact through the command line. Thus we must have basic Linux command line knowledge in order to expedite our work. In this article, I will explain some command lines that should be understood by beginners in interacting with Linux OS or UNIX based.

A command-line interface (CLI) processes commands to a computer program in the form of lines of text. The program which handles the interface is called a command-line interpreter or command-line processor. Operating systems implement a command-line interface in a shell for interactive access to operating system functions or services.

sudosudo allows a permitted user to execute a command as the superuser or another user, as specified by the security policy.  The invoking user’s real (not effective) user ID is used to determine the user name with which to query the security policy.
yumyum  is an interactive, rpm based, package manager. It can automatically perform system updates, including dependency analysis  and  obsolete  processing based on “repository” metadata. It can also perform installation of new packages, removal of old packages and perform queries  on  the  installed  and/or available  packages  among  many  other commands/services (see below). yum is similar to other high level package managers like apt-get and smart.
lsList  information  about  the FILEs (the current directory by default). Sort entries alphabetically if none of -cftuvSUX nor –sort is specified.
cdChange the current directory to dir.
pwdPrint the full filename of the current working directory.
mvRename SOURCE to DEST, or move SOURCE(s) to DIRECTORY.
cpCopy SOURCE to DEST, or multiple SOURCE(s) to DIRECTORY.
mkdirCreate the DIRECTORY(ies), if they do not already exist.
rmRemove files or directories, removes each specified file.  By default, it does not remove directories.
whoPrint information about users who are currently logged in.
clearclears  your  screen if this is possible.  It looks in the environment for the terminal type and then in the terminfo database to figure out how  to clear  the  screen.  Some terminals can clear also their scrollback uffer to prevent access to potentially sensitive data. 
systemctlThis command may be used to introspect and control the state of the “systemd” system and service manager.
firewall-cmdfirewall-cmd is the command line client of the firewalld daemon. It provides interface to manage runtime and permanent configuration.
nanonano  is  a  small,  free and friendly editor which aims to replace Pico, the default editor included in the non-free Pine package.  Rather than just copy‐ing  Pico’s  look and feel, nano also implements some missing (or disabled by default) features in Pico, such as “search and replace” and “go to line  and column number”.
tarUnzips tar archives(+more). GNU  `tar’  saves many files together into a single tape or disk archive, and can restore individual files from the archive.
unzipunzip will list, test, or extract files from a ZIP archive, commonly found on MS-DOS  systems.   The  default behavior (with no options) is to extract into
the current directory (and subdirectories below it) all files from the specified  ZIP  archive.  A companion program, zip(1L), creates ZIP archives; both programs are compatible with archives created by PKWARE’s PKZIP  and  PKUNZIP for  MS-DOS,  but in many cases the program options or default behaviors differ.
chmodChange file permissions. chmod changes the file mode bits of each given file according to mode, which can be  either  a  symbolic  representation of changes to make, or an octal number representing the bit pattern for the new mode bits.
chownChanges owner of a file or folder. chown changes the user and/or group ownership of each given file.  If only an owner (a user name  or numeric  user  ID)  is given, that user is made the owner of each given file, and the files’ group is not changed.  If the owner is followed by a colon and a  group  name  (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well.  If a colon but no group name follows the user name, that user is made the owner of the files and the group of the files is changed to that user’s login group.  If the colon and group  are given,  but  the owner is omitted, only the group of the files is changed; in this case, chown performs the same function as chgrp.  If  only  a  colon  is given,  or if the entire operand is empty, neither the owner nor the group is changed.
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