Types of shells

• Bourne shell (sh shell)
• C shell (csh shell)
• Z shell (zsh shell)
• Bourne again shell (bash shell)

linux commands

basic commands

1. echo - print a string
2. ls - list files in a directory
3. cd - change directory
4. pwd - print working directory
5. mkdir - make a directory
6. rmdir - remove a directory
7. rm - remove a file
8. cp - copy a file
9. mv - move a file
10. cat - concatenate files and print on the standard output
11. grep - search for a pattern in a file

User accounts

1. whoami - print the name of the current user
2. id - print the user ID of the current user
3. sudo - run a command as root
4. su - run a command as another user

Download files

1. curl <url> - download a file from the internet
2. wget <url> - download a file from the internet

Check OS version

1. uname -a - print operating system information
2. lsb_release -a - print operating system information

Package managers

RPM: Red Hat Package Manager

1. rpm -i <package> - install a package
2. rpm -e <package> - remove a package
3. rpm -q <package> - query a package

YUM: Yum Package Manager

1. yum install <package> - install a package
2. yum remove <package> - remove a package
3. yum list <package> - query a package
4. yum repolist - list available repositories

Services

1. service <service> start - start a service
2. systemctl start <service> - start a service
3. systemctl stop <service> - stop a service
4. systemctl status <service> - check the status of a service
5. systemctl enable <service> - enable a service to start at boot
6. systemctl disable <service> - disable a service to start at boot

VI editor

1. vi <file> - open a file in vi editor
2. to switch to insert mode: i
3. to switch to command mode: esc
4. to switch to visual mode: v
5. to switch to replace mode: r
6. to delete a character: x
7. to delete a line: dd
8. to delete a word: dw
9. to copy a line: yy
10. to paste a line: p
11. to save a file: :wq
12. to quit vi: :q
13. to quit vi without saving: :wq!
14. to quit vi and exit: :q!

Networking

1. ifconfig - print network interface configuration
2. route - print routing table
3. netstat - print network statistics
4. ping <host> - send ICMP echo request to a host
5. traceroute <host> - trace the route to a host
6. dig <host> - query DNS information
7. nslookup <host> - query DNS information
8. nmap <host> - scan a network
9. ss - print network statistics

Routing

1. route add -net <network> <gateway> - add a route
2. route del -net <network> - delete a route
3. route add -host <host> <gateway> - add a route