NFS stale error

why are we getting stale error ? and do we know when we get this ?

Not sure when they were in stale error. But to fix remount is the option.

A Stale file handle occurs when the file handle currently in use by a client is no longer recognized by an NFS server.  The typical case is that the file has been removed.  It is also possible that this may occur if the file has been deleted and recreated with the same name in the same directory.   The newly created file would have different filesystem meta-data associated with it, and therefore a different NFS file handle.   

fix  :- remount the filesystem

#umount <mount point>

#mount <mount point>


If you have issue with unmount the file system  refer the below link.
http://www.linuxtechnotes.com/2015/10/umount-mnt-device-is-busy-in-some-cases.html