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Fixing Warning: exec() href='function.exec'>function.exec</a>: Unable to fork [df -T -t nfs reported in http://forum.piwik.org/read.php?2,99550
Fixed in 
Could you help explain how you fixed this? (Warning: exec: Unable to fork [...])
I recently faced it but couldn't search for a solution.
(I'm newbie here and don't know how to browse the source of this commit.)