I have two directories (a and b), which are NFS shares with files foo.txt and bar.txt:I want merge this two directories to directory merge (does not have to be writable)this is possible by command:sudo mount -t overlay -olowerdir=a:b overlay mergeAt first sight everything is ok:. a    foo.txt b    bar.txt merge     bar.txt     foo.txtBut i can not read content of files:$ cat merge/foo.txt cat: merge/foo.txt: No such device or addressThis occurs only  on NFS share, on plain FS no problem.According to documentation https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt:An overlay filesystem combines two filesystems - an 'upper' filesystem  and a 'lower' filesystem.A read-only overlay of two read-only filesystems may use any  filesystem type.So I guess NFS is not a problem.
Merge two NFS shares with OverlayFS
nfs;overlayfs
What kernel are you using? it seems that a bug was introduced in kernel 4.2:https://github.com/coreos/rkt/issues/1537