Use lazy or force argument when unmounting filesystems

[zavocc]

Ideally using force or lazy arguments in umount ensures that all mountpoints are detached safely or forcibly so that the busy device can be unmounted before removal of the filesystem has been started

Lazy ensures safe unmount when a process constantly looks after it results in busy device, or force if the processes don't usually write something in the device nodes, whichever is sensible first

https://github.com/FerryAr/lhroot/blob/master/system/bin/killlinux

https://superuser.com/questions/412109/lazy-umount-or-unmounting-a-busy-disk-in-linux