linux usage: see firewall-cmd man page

Firewall-cmd is a command-line tool used to configure the firewall settings in Linux systems. Here are some basic usage examples:

1. To check the current status of the firewall:

`firewall-cmd --state`

2. To view all active zones:

`firewall-cmd --get-active-zones`

3. To add a new service to a zone:

`firewall-cmd --zone=public --add-service=http`

4. To allow incoming traffic for a specific port:

`firewall-cmd --zone=public --add-port=80/tcp`

5. To remove a service or port from a zone:

`firewall-cmd --zone=public --remove-service=http`

6. To reload the firewall configuration:

`firewall-cmd --reload`

For more detailed information and advanced usage, please refer to the firewall-cmd man page by typing `man firewall-cmd` in the terminal.