New beginners guide to firewalld

[sspencerwire]

• tested rules using an LXD container
• did an editing pass checking word usage, commas, and general feel
• would really, really, really like some input on this

Author checklist (Completed by original Author)

• Contribution a good fit for the Rocky project? Title and Author MetaTags inserted ?
• Is this a non-English contribution?
• If applicable, steps and instructions have been tested to work on a real system
• Did you perform an initial self-review to fix basic typos and grammatical correctness

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Check that document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Basic Editorial Review)
• 4th Pass (Detailed Editorial Review and Peer Review)
• Final pass/approval (Final Review)

[sspencerwire]

I would love someone to review this with a technical eye, particularly if you have experience using firewalld. Please add your comment and suggestions!

[EzequielBruni]

Alright, I gave it an editing pass, adding some bits I thought might be useful. I only have one overall piece of feedback: this isn't strictly a beginner's guide to firewalld, so much as it is an iptables user's guide to firewalld. Maybe we should change the title to reflect that?

Later on, I could take a lot of what's here and give it the absolute newbie treatment if y'all think that would be good.

[alemorvan]

Could we add a paragraph with instructions on how to check firewall state ?

Something like this:

Remember to check the status of your firewall with either :

the command firewall-cmd:

$ firewall-cmd --state
running

the systemctl command:

$ systemctl status firewalld

[alemorvan]

I like the Common firewall-cmd Commands table 👍

[alemorvan]

What about adding a paragraph about testing if a port is open ?
The tool to do that (forgive telnet 🙏 ) is netcat (nc).
For example:

nc -zv 192.168.1.10 22

The -u option is use to test udp port.

[alemorvan]

Testing connections

System administrators are very fond of the telnet command to perform their tests and verify that a port is open and accessible.

Today, the recommended command is nc (netcat) which you can use as follows:

nc -zv 192.168.1.10 22

The -u option is use to test udp port by the same way.