GSoC Idea: per-process filesystem namespaces for FreeBSD

Rodney W. Grimes freebsd-rwg at
Wed Mar 14 01:25:59 UTC 2018

> > On Mar 13, 2018, at 7:16 PM, Warner Losh <imp at> wrote:
> > 
> > 
> > 
> >> On Tue, Mar 13, 2018 at 4:31 PM, Mark Saad <nonesuch at> wrote:
> >> 
> >>> On Mar 13, 2018, at 5:43 PM, Warner Losh <imp at> wrote:
> >>> 
> >>>> On Tue, Mar 13, 2018 at 1:55 PM, Kristoffer Eriksson <ske at> wrote:
> >>>> 
> >>>> 
> >>>>> On 13 Mar 2018 12:53:18, Theron <theron.tarigo at> 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 .

If you have any questions I am happy to share my working tooling.


isc-dhcp from ports,
base system tftp setup via inetd
some bits of syslinix 6.03
proper set of iPXE.exe binaries built with iSCSI, http and nfs support,
you wont need iSCSI, I use that for other things like Windblows.
I boot direct from iPXE to nfs loaded kernel, only thing tftp is used
for is getting a modern version of iPXE onto the booting system.

iPXE loads a menu.ipxe to allow OS selection.
menu.ipxe loads /boot/pxeboot via NFS
YOU SHALL HAVE ISSUES HERE most pxeboot images are broken
pxeboot loads kernel via NFS
kernel runs, end up in /etc/rc.diskless that does the rest of the magic.

Rod Grimes                                                 rgrimes at

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