OverlayFS has a workdir
option, beside two other directories lowerdir
and upperdir
, which needs to be an empty directory.
Unfortunately the kernel documentation of overlayfs does not talk much about the purpose of this option.
The "workdir" needs to be an empty directory on the same filesystem as upperdir.
For readonly overlays the workdir
might be ommittet among the upperdir
. This give me the clue that it has to do with writing the merged files.
Please explain what's happening in the workdir
when files are written or changed in the merged directory. Why is the writable upperdir
not enough?