Date: Mon, 24 Feb 2014 13:46:08 -0600 From: Brooks Davis <brooks@freebsd.org> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-filesystems@freebsd.org, freebsd-hackers@freebsd.org, Jordan Hubbard <jordan.hubbard@gmail.com>, Willem Jan Withagen <wjw@digiware.nl>, Perry Hutchison <perryh@pluto.rain.com> Subject: Re: Thoughts on Multi-Symlink Concept Message-ID: <20140224194608.GD18404@lor.one-eyed-alien.net> In-Reply-To: <alpine.BSF.2.00.1402241828000.61905@fledge.watson.org> References: <CAO2cuEMC==HstC4VkkiFpHyo6LA_xyCjYKvCEECXneVLNnZpZg@mail.gmail.com> <A31B3F88-861F-459B-AD67-F146D5514594@mail.turbofuzz.com> <530049a1.XXZ1PjZFgRyCu9X6%perryh@pluto.rain.com> <53092D83.6050603@digiware.nl> <43505B61-FAE8-4A61-922E-78F6007BBFC3@gmail.com> <alpine.BSF.2.00.1402241828000.61905@fledge.watson.org>
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--zCKi3GIZzVBPywwA Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Feb 24, 2014 at 06:31:08PM +0000, Robert Watson wrote: > On Sat, 22 Feb 2014, Jordan Hubbard wrote: >=20 > >> Yes, please can we get these .... > >> > >> Apollo Domain systems had those, and they were great. Set SYSTYPE to B= SD4=20 > >> and get the BSD tree and all that came with it, or SYSV to get the oth= er=20 > >> stuff. > > > > Yep, I loved these things on Domain/OS! We system admin types used the= m to=20 > > do all kinds of clever (and useful) things. > > > > Looks like FreeBSD has actually *had* an implementation for 6 years now= =2E I=20 > > don?t necessarily agree with the architectural decision to create a=20 > > different namespace and command (varsym) to manipulate it - it was real= ly=20 > > nice just having it be a part of the standard environ(7) - but hey, any= =20 > > implementation is better than no implementation. Whatever happened to= =20 > > https://wiki.freebsd.org/200808DevSummit?action=3DAttachFile&do=3Dget&t= arget=3Dvariant-symlinks-for-freebsd.pdf=20 > > ? >=20 > Some care is required here: at least one of the past implementations floa= ting=20 > around had the neat property that user-defined symlink expansions occurre= d=20 > before system-defined ones, even for setuid binaries. This allowed trivi= al=20 > replacement of libraries out from under a binary, making rooting boxes ea= sy.=20 > I'm actually a fan of variant symlinks as well, having used them in AFS -= - I'd=20 > just prefer we aim for a model that minimises inconvenient rooting of box= es.=20 > (I'm not passing judgement on this particular patch, mind you.) I believ= e=20 > Brooks Davis did the last serious pass at variant symlinks and might opin= e=20 > further on the topic. The version I wrote worked find last time I ported it forward (20 months or so ago). There's a copy in svn that's the latest. The thing that's held me back from committing it is lack to time to do some solid macro and micro benchmarks to determine what the performance impact is when it's compiled in, but disabled. It should probably just be updated, reviewed by a VFS person and committed. I believe I've successfully avoided the pitfalls Robert describes. -- Brooks --zCKi3GIZzVBPywwA Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (FreeBSD) iKYEARECAGYFAlMLoX9fFIAAAAAALgAoaXNzdWVyLWZwckBub3RhdGlvbnMub3Bl bnBncC5maWZ0aGhvcnNlbWFuLm5ldDY1NUQ1MTlDMjZBNzgyRTcyNTI5OUJGMDVE OEU4QkU5RjIzODFBRDQACgkQXY6L6fI4GtSO0QCg44VpZO1+EJ4lMnhMFaFoiMLh O7MAnRC1zEZwNryohiAx27k+XfFbXn/M =ldgi -----END PGP SIGNATURE----- --zCKi3GIZzVBPywwA--
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