Script mining on old Linux Machines - Help?

So it's been about a year since I've done any litecoin/bitcoin mining (lost about $1000 worth of crypto so I gave it all up) and since then I've accumulated several older machines that could be put to good use. So could anyone get me up to speed on the whole crypto-mining situation (what good coins to cpu mine, etc.)? Also I have never mined on a Linux machine before so I could use some help there as well.

Not really concerned about power costs, my house has solar panels which usually provide an excess of power each month (we get a check from the power company :D) and since it being the winter I don't mind the extra heat from some machines running hard. 


Not really worth the time to setup. In my opinion the only CPU friendly coin right now is Dogecoin and you'd probably get like ~10 coin a day (not worth it when dual GPU miners are doing ~30k)