/usr/sbin/opendkim-genkey: No such file or directory

/usr/sbin/opendkim-genkey: No such file or directory

The error is created by the a non existing file "opendkim-genkey" in /usr/sbin/

To solve this run 
"sudo yum install opendkim-tools" on centos
"sudo apt-get install opendkim-tools" on ubuntu

After this go to the folder /usr/sbin/ you should see your newly generated file