Linux command with Interview Questions and Answers for System Administrator and developer freshers and experienced

The Linux operating system was conceived and implemented in 1969 at AT&T's Bell Laboratories in the United States by Ken Thompson, Dennis Ritchie, Douglas McIlroy, and Joe Ossanna. It was first released in 1971 and was initially entirely written in assembly language, a common practice at the time. Later, in a key pioneering approach in 1973, Unix was re-written in the programming language C by Dennis Ritchie. The availability of an operating system written in a high-level language allowed easier portability to different computer platforms. With a legal glitch forcing AT&T to license the operating system's source code,linux quickly grew and became widely adopted by academic institutions and businesses.

A word List formed a command LS that show contents of home directory like below
$ ls ~
To show everything in a vertical column used like below
$ ls -al
it will show like below
drwxr-xr-x 5 root root 3090 Jun 19 20:39 boot/
drwxr-xr-x 8 root root 4509 Jul 21 09:56 dev/
drwxr-xr-x 94 root root 4096 Jul 12 10:35 etc/
show directories in the current directory
$ ls -d */
show ALL subdirectories
$ ls *

mkdir
Create new folder or directory, if they do not already exist already
syntex like below
mkdir [Options] directories
OPTIONS
-m, --mode=MODE set permission mode (as in chmod), not rwxrwxrwx - umask
-p, --parents no error if existing, make parent folder as needed
mkdir creates the standard entries . (dot) for the current folder
and .. (dot dot) for its parent
cd used for Change Directory
rm To Remove files
rmdir To Remove folder(s)