GSoC Idea: per-process filesystem namespaces for FreeBSD

Mark Saad nonesuch at
Tue Mar 13 22:31:45 UTC 2018

> 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 .

Mark Saad | nonesuch at

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