System Basic Commands

 IP Commands:
hostname
hostname -i     //Display the IP address(es) of the host
ifconfig
hostname -a     //Display the alias name of the host
hostname -d     //Display the name of the DNS domain

OS Commands:
uname
uname -a
arch
cat /etc/redhat-release
cat /etc/os-release

Date Commands:
date
date +%a     //locale’s abbreviated weekday name (e.g., Sun)
date +%A     //ocale’s full weekday name (e.g., Sunday)
date +%b     //locale’s abbreviated month name (e.g., Jan)
date +%B     //locale’s full month name (e.g., January)
date +%d     //day of month (e.g, 01)
date +%D     //date; same as %m/%d/%y
F     //full date; same as %Y-%m-%d
u     //day of week(1 is monday)
U    //week number of year
H    //hours(00..23)k(0..23)
I     //hours(01..12)l(1..12)
M     //minute
S     //seconds
m     //month
Y     //year(2020)y(last 2 digit(20))

Calendar Commands:
cal    //current month calender
cal 2010     //2010 calender
cal 5 2010     //2010 may month calender
cal -3     //Display prev/current/next month output.

Disk Commands:
du dir_name or file_name     //bytes in file space usage
du -h     //human readable
df
df -h
free     //free and used memory in the system
free -b     //bytes
free -k  //KB
free -m     //MB
free -g     //GB

User Commands:
logname     //name of the current user
whoami     //name of the current user
who am i     //current user name and login time
who     //show who is logged on
who -u     //show who is logged on with ip address
id     //user and group information
users    //user names of users currently logged in to the current host
groups     //group memberships for each username
groups group_name
uptime     //Tell how long the system has been running

w     //Displays information about the users currently on the machine and their processes

wall     //Send a message to everybody’s terminal
history     //System Basic CommandhistoryDisplay the command history list
history -c     //clear the history
clear     //Clear the terminal screen
alias clr=clear     //create alias string for command with option
alias     //list of all alias
unalias clr     //remove alias
expr 10 + 20     //addition,sub,mul,devision,models
seq 10     //Display a sequence of numbers
seq 1 10
seq 2 2 10
vmstat
iostat
netstat
sleep 10     //Pause for a specified amount of time(seconds)
ping
echo 'welcome'