Subject: Re: Union mount problem?
To: None <current-users@NetBSD.ORG>
From: der Mouse <mouse@Collatz.McRCIM.McGill.EDU>
Date: 10/30/1995 08:49:05
>> Is the upper layer a 4.4 filesystem?
>> 4.2 & 4.3 filesystems do not support whiteouts, which unionfs needs.
> What I don't understand is, why does the upper layer *need* to
> support whiteouts in order to be mounted rw? If it doesn't you can't
> create whiteouts, fine, but you can still alter files in the lower
> layer or write new ones.
But not remove files which exist in the lower layer. I know _I_ would
be rather surprised to find I could overwrite a file, create new files
to my heart's content, but be unable to remove some files.
I was rather astonished to discover that the unionfs (mis)behaved this
way, demanding whiteout support. IMO it should keep metadata files
instead, the way Sun's tfs does. I have a user-level implementation of
such a filesystem, but it looks to the kernel like an NFS mount, and
lots of things simply don't work over NFS. I tried to do a build of
the world on it and I got just too much brokenness. Once NFS really
works I'll probably try again.