Displaying Information for Nested File Systems with the DF tool
When a file system mounts on top of another file system, the command df -a does not display the attributes for the covered file system.
On Linux environments, this is the expected behavior for any file system that is overlayed by another file system.
The secfs driver properly handles the call, which is made by the statfs system call, which is issued by the df tool. When the system call returns, its structures are correctly populated with the details of the nested file system. On examining the source of the df tool, it is found that when the -a switch is on, it nullifies the stats which are received for overlayed mounts. When the -a option is not enforced, the stats are maintained.
Issue the df command for a specific mount point, for example df /xfs/nested-xfs (where /xfs is a secfs GuardPoint). It works correctly.
