GSoC Idea: per-process filesystem namespaces for FreeBSD

[Mark Saad]

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