[CentOS] unable to umount

> nothing is using the partition
> $ lsof |grep srv
> <empty>

Although the prompt is a $, I assume you're actually doing this as root?

> $ umount /srv
> umount: /srv: device is busy
> umount: /srv: device is busy
> 
> 
> what could keeping the device "busy" ... ?

Is the device NFS exported?  I've seem that prevent umounting even though
nothing shows up in the process list.

-- 

rgds
Stephen