[ Just stumbled on this on the mail archive. ]


On Tue, 2016-02-16 at 08:42:07 +0100, Jérémy Bobbio wrote:
> Steven Chamberlain:
> > On linux, a symlink can only have permissions 0777 (lrwxrwxrwx)
> > 
> > But on at least kfreebsd (maybe hurd?) there is no such limitation, and
> > permissions are set like any regular file.  That also means the umask is
> > applied...  and tar and dpkg-deb preserve this.

Yes, Hurd too. Linux probably is the odd one here.

> > This proves to be an issue for:
> >   * reproducible builds on kfreebsd, affected by user's umask
> >   * reproducing arch:all packages between linux<->kfreebsd
> >   * reproducing linux packages by cross-building from kfreebsd
> > 
> > I think we should normalise symlinks' permissions to 0777, except GNU
> > chmod can't do that!  (chmod follows the symlink, and has no -h flag).
> > 
> > Adding a -h (no dereference) option to chmod would allow dh_fixperms to
> > use that.  But (as pointed out in #759886) adding things there does not
> > help packages not using debhelper, or other uses of tar.
> > 
> > Would this be best added as a feature to tar, that dpkg-deb can use?
> > Probably a new flag, that would apply --mode a=rwx only to symlinks.
> > 
> > Or are there other ideas how to fix this?

I noticed this due to the dpkg test suite, and fixed it by temporarily
setting umask to 0:


And added it to the wiki:


> One idea floating is to get dpkg-deb working with an explicit manifest
> to create the package content. I believe that would solve the issue. But
> that's at least mid-term because dpkg needs to get its own Tar
> implementation (or maybe depend on libarchive) and, likely harder, a
> format needs to be defined for the manifest.


> In the meantime, shouldn't GNU chmod get a `-h` option in any cases if
> it's going to be used on kFreeBSD?
> Then it's pretty easy to start with `dh_fixperms` and see how much it
> helps.
> Guillem said he was ok with dpkg depending on recent versions of
> Tar[1], but changes would need to be accepted by Tar upstream.

Yes, if you get a new option in tar I'm fine using it. But given the
reaction to the --clamp-mtime option, this might not fly with upstream?
(Also it seems the patch for that one might have been better sent to
bug-tar instead of help-tar.)

> What's the situation regarding symlinks on HURD?

See above.

>  [1]:?https://bugs.debian.org/759886#73


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