Add support for rotational#26

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stanleyz wants to merge 8 commits intoevenup:masterfrom

stanleyz:master

Commits on Sep 8, 2016

can't believe I didn't commit
Stanley Zhang
committed

Commits on Sep 17, 2016

obviously the is_integer function in 3.2.0 doesn't work
Stanley Zhang
committed
there seems no centos-65 any more replaced with centos-66
Stanley Zhang
committed
a copied issue and use value comparison
Stanley Zhang
committed

Commits on Dec 13, 2016

use hdparm to control writecache
Stanley Zhang
committed
CentOS 7 requires the rc.local to be executable
Stanley Zhang
committed
use rc.d/rc.local cause /etc/rc.local is just a symlink
Stanley Zhang
committed

Commits on Apr 6, 2017

make it work with right idea of fail_on_missing
stanleyz
committed