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 merge

At first sight everything is ok:

├── a
│   └── foo.txt
├── b
│   └── bar.txt
└── merge
    ├── bar.txt
    └── foo.txt

But i can not read content of files: $ cat merge/foo.txt cat: merge/foo.txt: No such device or address

This 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.

1 Answer 1


What kernel are you using? it seems that a bug was introduced in kernel 4.2:


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