RHEL CentOS set default editor to NANO
VI is a wonderful, full feature text editor. However, some might lack experience with VI and prefer a simpler text editor for quick configuration and other edits.
Install nano
yum -y install nano
System Default Editor
cat <<EOF >>/etc/profile.d/nano.sh
export VISUAL="nano"
export EDITOR="nano"
EOF
User Default Editor
cat <<EOF >>~/.bash_profile
export VISUAL="nano"
export EDITOR="nano"
EOF