Quickly add rules to IPTABLES on CentOS/RHEL 5.x using a script

Older iptables lack the -C switch so you have to use bash to check whether a rule already exists before appending it. Works like this:

if [ ! "`iptables-save | grep 'dport 21'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT;fi
if [ ! "`iptables-save | grep 'dport 22'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT;fi
if [ ! "`iptables-save | grep 'dport 80'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT;fi
service iptables save

Probably not the most elegant solution, but it works. 

Quickly disable SELinux in a setup script

So we all know how to disable SELinux manually, but what about doing so as part of a setup script?
Easy, got to love sed!

Setenforce 0

sed -i 's/^SELINUX=.*/SELINUX=disabled/g' /etc/sysconfig/selinux && cat /etc/sysconfig/selinux

Repeat on /etc/selinux/config for Centos 7