_System Based Commands

#uname Displays Linux system information

#uname -rDisplays kernel release information

#uptimeDisplays how long the system has been running

#hostnameShows the system hostname

#hostname -iDisplays the IP address of the system

#last rebootShows system reboot history

#dateDisplays current system date and time

#whoamiDisplays who you are logged in as

#finger usernameDisplays information about the user

_Hardware Based Command

#lshw Displays information about system’s hardware configuration

#lsblkDisplays block devices related information

#free -mDisplays free and used memory in the system (-m indicates memory in MB)

_Users Management Commands

#idDisplays the details of the active user e.g. uid, gid, and groups

#lastShows the last logins in the system

#whoShows who is logged in to the system

#groupadd "pink"Adds the group ‘pink’

#adduser "rajni"Adds user ‘rajni’

#userdel "rajni"Deletes user ‘rajni’

#usermodUsed for modifying user information

_File Commands

#ls -alLists files – both regular & hidden files and their permissions

#pwdDisplays the present working directory path

mkdir 'pink'Creates a new directory named ‘pink’

#rm file_nameRemoves a file

#rm -f filenameForcefully removes a file

#rm -r directory_nameRemoves a directory recursively

#rm -rf directory_nameRemoves a directory forcefully and recursively

#cp file1 file2Copies the contents of file1 to file2

#cp -r dir1 dir2Recursively Copies dir1 to dir2. dir2 is created if it does not exist

#mv file1 file2Renames file1 to file2

#ln -s /path/to/file_name link_nameCreates a symbolic link to file_name

#touch file_nameCreates a new file

#cat > file_namePlaces standard input into a file

#more file_nameOutputs the contents of a file

#head file_nameDisplays the first 10 lines of a file

#tail file_nameDisplays the last 10 lines of a file

#gpg -c file_nameEncrypts a file

#gpg file_name.gpgDecrypts a file

#wcPrints the number of bytes, words and lines in a file

#xargsExecutes commands from standard input

_Process Related Commands

#psDisplay currently active processes

#ps aux | grep 'telnet'Searches for the id of the process ‚telnet‘

#pmapDisplays memory map of processes

#top Displays all running processes

#kill pidTerminates process with a given pid

#killall procKills / Terminates all processes named proc

#pkill process-nameSends a signal to a process with its name

#bgResumes suspended jobs in the background

#fgBrings suspended jobs to the foreground

#lsofLists files that are open by processes

_File Permission Commands

chmod octal filename Change file permissions of the file to octal

Example

#chmod 777 peep.txtSet rwx permissions to owner, group and everyone

#chmod 755 peep.txt Set rwx to the owner and r_x to group and everyone

#chmod 766 peep.txt Sets rwx for owner, rw for group and everyone

#chown owner user-file Change ownership of the file

#chown owner-user:owner-group file_name Change owner and group owner of the file

#chown owner-user:owner-group directory Change owner and group owner of the directory

_Network Commands

#ip addr show Displays IP addresses and all the network interfaces

#ip address add 192.160.0.1/24 dev eth0 Assigns IP address 192.168.0.1 to interface eth0

#ifconfig Displays IP addresses of all network interfaces

#ping host ping command sends an ICMP echo request to establish a connection to server

#whois domain Retrieves more information about a domain name

#dig domain Retrieves DNS information about the domain

#host google.com Performs an IP lookup for the domain name

#hostname -i Displays local IP address

#wget file_name Downloads a file from an online source

#netstat -pnltu Displays all active listening ports

_Compression/Archives Commands

#tar -cf peep.tar peep<:code>Creates archive file called ‚peep.tar‘ from file ‚peep‘

#tar -xf peep.tar Extract archive file ‚peep.tar‘

#tar -zcvf peep.tar.gz source-folder Creates gzipped tar archive file from the source folder

#gzip file Compression a file with .gz extension

_Install Packages Commands

#rpm -i pkg_name.rpm Install an rpm package

#rpm -e pkg_name Removes an rpm package

#dnf install pkg_nameInstall package using dnf utility

_Search Commands

#grep 'pattern' files Search for a given pattern in files

#grep -r pattern dir Search recursively for a pattern in a given directory

#locate file Find all instances of the file

#find /home/ -name "index" Find file names that begin with ‚index‘ in /home folder

#find /home -size +10000kFind files greater than 10000k in the home folder

_File Transfer Commands

#scp file1.txt server2/tmp Securely copy file1.txt to server2 in /tmp directory

#rsync -a /home/apps /backup/ Synchronize contents in /home/apps directory with /backup directory

_Disk Usage Commands

#df -h Displays free space on mounted systems

#df -i Displays free inodes on filesystems

#fdisk -l Shows disk partitions, sizes, and types

#du -sh Displays disk usage in the current directory in a human-readable format

#findmnt Displays target mount point for all filesystems

#mount device-path mount-pointMount a device

_Directory Traverse Commands

#cd .. Move up one level in the directory tree structure

#cd Change directory to $HOME directory

#cd /test Change directory to /test directory