File System Operations 

• ls - List Directory Contents 

• cd - Change directory 

• pwd - Print name of current directory 

• mkdir - Make directories 

• cp - Copy files and directories 

• mv - Move/rename files and directories 

• rm - Remove files or directories

• touch - Create an empty file 

• cat - Concatenate and display file content 

• nano - Text editor for creating/editing files

• vim - Text editor VIM 

 File Permission 

• chmod - Change file permissions

• chown - Change file owner and group

• chgrp - Change group ownership of files 

 Process Management 

• ps - Report a snapshot of current processes

• top - Dynamic real-time view of running process

• kill - Terminate a process

• killall - Terminate processes by name 

 File Transfer

• scp - Secure Copy (remote file copy program) 

• rsync - Remote file synce 

 Package Management

• apt-get - Package handling utility (Debian-based) 

• yum/dnf - Package handling utility (RPM-based) 

• dpkg - Package manager for (Debian-based) system 

• rpm - Package manager for (RPM-based) systems 

 System Services

• systemctl - Control the systemed system

• service - Run a system V init script 

• chkconfig - Updates and queries run level information for system services

 User and Group Management

• useradd - Create a new user 

• usermod - Modify a user account 

• userdel - Delete a user account 

• groupadd - Create a new group

• groupmod - Modify a group 

• groupdel - Delete a group 

 Networking

• ifconfig - Configure Network interfaces 

• ping - Test network connectivity

• netstat - Print network connections, etc.

• iptables - Packet filtering and NAT

 System Information

• uname - Print system information 

• df - Report file system disk space usage 

• free - Display amount of free and used memory 

• hostname - Print or set the system's hostname 

 Shell Scripting

• bash - GNU Bourne-Again Shell 

• sh - Original UNIX shell

• awk - Pattern scanning and processing language

• sed - Stream editor for filtering & transforming text