This Gist contains Basic Linux Utilities and System information related commands and their meaning, this gist's sole purpose is to help students learn basic file management commands.

Learn Linux Basics | Part 3: Basic Linux Utilities and System information related commands

Basic Linux Utilities:

man <name> - Read the manual page of <name>

man <section> <name> - Read the manual page of <name>, related to the given section. 

man -k <editor> - Output all the software whose man pages contain <editor> keyword.

man -K <keyword> - Outputs all man pages containing <keyword> within them.

apropos <editor> - Output all the applications whose one line description matches the word editor. When not able to recall the name of the application, use this command.

help - In Bash shell, this will display the list of all available bash commands.

help <name> - In Bash shell, this will display the list of all available bash commands. 

info <name> - View all the information about <name>.

dpkg -l - Output a list of all installed packages on a Debian-based system.

dpkg -L packageName - Will list out the files installed and path details for a given package on Debian.

dpkg -l | grep -i <edit> - Return all .deb installed packages with <edit> irrespective of cases.

less /var/lib/dpkg/available - Return descriptions of all available packages.

whatis vim - List a one-line description of vim.

<command-name> --help - Display usage information about the <tool-name>. Sometimes command       -h also works, but not for all commands.

User identification and who is who in Linux world:

hostname  - Display hostname of the system.
hostname -f - Displays Fully Qualified Domain Name (FQDN) of the system.
passwd - Change password of current user.
whoami - Username of the users logged in at the terminal.
who - List of all the users currently logged in as a user.
w - Display current system status, time, duration, list of users currently logged in on system and other user information.
last - Who recently used the system.
last root - When was the last time root logged in as user.
lastb - Shows all bad login attempts into the system.

Process related information:
top - List all processes sorted by their current system resource usage. Displays a continually updated display of processes (By default 3 seconds). Use q key to exit top.
ps - List processes currently running on current shell session
ps -u root - List all of the processes and commands root is running
ps aux - List all the processes by all users on the current system

Detecting Linux distribution name and version:
On Debian:
lsb_release -a

On Ubuntu:
lsb_release -a

If lsb_release not installed then try: 
cat /etc/issue

Detect what systemd-based distribution os have run:
cat /etc/os-release
(for red-hat run: cat /etc/redhat-release)

Print information about the current system:
uname [OPTION]
e.g. -a or --all - Prints all information, omitting -p and -i if the information is unknown.
run: 
uname -a
All The options:
-s, --kernel-name - Print the kernel name.
-n, --nodename - Print the network node hostname.
-r, --kernel-release - Print the kernel release.
-v, --kernel-version - Print the kernel version.
-m, --machine - Print the machine hardware name.
-p, --processor - Print the processor type, or "unknown".
-i, --hardware-platform - Print the hardware platform, or "unknown".
-o, --operating-system - Print the operating system.
--help - Display a help message, and exit.
--version - Display version information, and exit.

Find your linux os (both debian & rpm) name and release number:
cat /etc/*release




Note: If you want to try above commands without any risk, use Docker, so install docker and use below docker commands to run a Linux cotainer and use the shell, e.g. as in tutorial I have shown:
docker run -it ubuntu:16.04 /bin/bash 
But you can use any linux OS , it's your choice. Docker Tutorial Link: https://www.youtube.com/watch?v=Y56FMHC1mb8