Bug 195113

Summary:	overlayfs documentation appears to be wrong
Product:	File System	Reporter:	bluescreen_avenger
Component:	Other	Assignee:	fs_other
Status:	NEW ---
Severity:	normal	CC:	fgrose, leonard.r.koenig
Priority:	P1	Keywords:	trivial
Hardware:	All
OS:	Linux
Kernel Version:	4.10	Subsystem:
Regression:	No	Bisected commit-id:

Description bluescreen_avenger 2017-03-28 03:28:51 UTC

Hi

 
It seems that according to https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt it says

    The lower filesystem can be any filesystem supported by Linux

However there appears to be filesystems that overlayfs does NOT support (such as vfat). If I try to use a vfat file system as the lowerdir, I get
    overlayfs: filesystem on '/tmp/lower' not supported
in my dmesg.

So now I am not sure what filesystems cannot be used as a lowerdir for overlayfs.
(or what conditions I need to check for... ...in userspace)


Thanks

Comment 1 Leonard/Janis Robert König 2019-11-01 17:09:20 UTC

I can confirm that overlayfs doesn't support vfat here either.

Comment 2 bluescreen_avenger 2020-07-02 01:10:00 UTC

The Documentation states
"The lower filesystem can be any filesystem supported by Linux and does
not need to be writable."

But FAT doesn't work as a lower file system. The documentation should be updated so it's not misleading