Date: Tue, 13 Mar 2018 20:00:00 -0400 From: Mark Saad <nonesuch@longcount.org> To: Warner Losh <imp@bsdimp.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>, Kristoffer Eriksson <ske@pkmab.se>, Theron <theron.tarigo@gmail.com> Subject: Re: GSoC Idea: per-process filesystem namespaces for FreeBSD Message-ID: <B0D77EC9-16C0-4A47-99CD-3F9B3FC5FC28@longcount.org> In-Reply-To: <CANCZdfq3J75k2GRvWa7k-n29VST6x00Pz1NUQAmwSMtfCSEOEQ@mail.gmail.com> References: <d7621074-acb4-c5b6-1efd-dc55b51586b1@gmail.com> <201803132055.aa28780@berenice.pkmab.se> <CANCZdfoU1B4228RpwfupvdVN9RPCCug4p283xmkNwW7t-M9CjA@mail.gmail.com> <BACCA158-AB12-4DE1-B70A-2084FF2C5806@longcount.org> <CANCZdfq3J75k2GRvWa7k-n29VST6x00Pz1NUQAmwSMtfCSEOEQ@mail.gmail.com>
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> On Mar 13, 2018, at 7:16 PM, Warner Losh <imp@bsdimp.com> wrote: > > > >> On Tue, Mar 13, 2018 at 4:31 PM, Mark Saad <nonesuch@longcount.org> wrote: >> >>> On Mar 13, 2018, at 5:43 PM, Warner Losh <imp@bsdimp.com> wrote: >>> >>>> On Tue, Mar 13, 2018 at 1:55 PM, Kristoffer Eriksson <ske@pkmab.se> wrote: >>>> >>>> >>>>> On 13 Mar 2018 12:53:18, Theron <theron.tarigo@gmail.com> wrote: >>>>> For those unfamiliar with Plan9, here is a rough explanation of the >>>>> namespace feature: unlike in Unix, where all processes share the same >>>>> virtual filesystem, each process instead has its own view of the >>>>> filesystem according to what has been mounted ... >>>> >>>> What if I mount a new /etc with a passwd file where root has no >>>> password, and then run "su"? >>>> >>>> (How does Plan9 handle that?) >>>> >>> >>> Plan9 handles that by having a daemon that does user authentication. It's >>> actually more complicated than that, but the machine owner has control over >>> who can do what. For this to work in FreeBSD, either we'd need to disallow >>> the 'file' type for passwd, or we'd have to do something sensible with >>> setuid programs. Well, maybe not 'or' but 'and' since the security of >>> setuid programs depends on the security of the filesystem.... Plan 9 >>> doesn't have these complications, so it can offer a user malleable >>> filesystem without security risk. >>> >>> Warner >> >> A kind of related task; FreeBSD could benefit from : Fixing and improving unionfs / nullfs. There are some weird issues with the current unionfs and while it works in many cases there are some edge cases where the comments are something like “ FreeBSD needs a proper stacking vfs ...” the examples I can think of ; imagine you have a jail , chroot or even a Pxe booted system where you want a a read only null mount from the hosts /bin to the targets /bin . Now expand that to most of the base system and the mount tmpfs’s for /tep /var/log etc. most of that works but try to unmount it in the wrong order or thrash a unionfs with lots of writes ,on top of a tmpfs and things break . >> So to be clear the project would be to better document the various uses of unionfs and nullfs that work , for the ones that do not diving into the stacking vfs and seeing if it could be implemented and if it would help . >> >> Alternatively making FreeBSD multiboot compliant would rock . This would allow FreeBSD to natively boot from ipxe or syslinux derivates; thus allowing you to boot a working FreeBSD install via a kernel and mfsroot image off a web server . > > There appears to already be a multiboot.c in the bootloader. I've been told by others in the past it just works... > > Warner I am going down the rabbit hole to see how it works . However I still think the unionfs / nullfs work I mentioned before would be a good project related to the plan9 idea in some ways . --- Mark Saad | nonesuch@longcount.org
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