Subject: Re: union mount directory permissions
To: None <tech-kern@NetBSD.org>
From: Chapman Flack <firstname.lastname@example.org>
Date: 09/27/2004 23:15:57
> * policy: when creating the shadow directory in the
> * upper layer, create it owned by the user who did
> * the mount, group from parent directory, and mode
> * 777 modified by umask (ie mostly identical to the
> * mkdir syscall). (jsp, kb)
> uhm.. so, why? File permissions and ownership are copied. Shouldn't
> directories behave the same?
Count this as a "me too". I had big plans for things I was going to do
with union mounts, but scrapped them because I can't trust the shadow
copies to have the right permissions. I don't understand the reasoning.
There's also (what seems to be) a bug (I haven't tried anything more recent
than 1.6.2 i386) with shadow-copying a file when the underlying FS is readonly.
Trying to open the existing file for writing produces EROFS instead of
making a shadow copy ... but putting a union mount over a readonly file
system is one of the most obvious uses of union mounts .... Creating a
*new* file works fine, and shadow copying the file works fine if the below
FS isn't readonly.