Install firewalld Centos7

Trying to reproduce a client problem I was following these instructions and ran into firewalld not being installed.

[root@localhost ~]# sudo firewall-cmd --permanent --add-service=http
sudo: firewall-cmd: command not found
[root@localhost ~]#

After installing and enabling firewalld the installation could continue.

Before you merging this, please consider

Would it not be better for the user if we install everything in one command at the beginning like this:

sudo yum install curl openssh-server postfix firewalld

I assumed there might be a reason not to since we already install postfix in it's own command.