Start, enable, stop and disable firewalld on Centos

Start firewalld  service run nex commands:

systemctl unmask --now firewalld

systemctl enable firewalld

systemctl start firewalld

Stop firewalld  service run nex commands:

systemctl stop firewalld

sudo systemctl disable firewalld

sudo systemctl mask --now firewalld

References:

https://linuxize.com/post/how-to-stop-and-disable-firewalld-on-centos-7/

https://bobcares.com/blog/failed-to-start-firewalld-service-unit-is-masked/