GSoC Idea: per-process filesystem namespaces for FreeBSD

Mark Saad nonesuch at
Wed Mar 14 01:35:06 UTC 2018

On Tue, Mar 13, 2018 at 9:25 PM, Rodney W. Grimes
<freebsd-rwg at> wrote:
>> > 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.

I think you are both missing my point. I can boot FreeBSD with ipxe
loading mfsbsd style setups like this

initrd ${base-root}/freebsd/mfsroot.gz
chain ${base-root}/other/memdisk harddisk raw

I want to be able to boot and run it like I would Linux or ESXi with
the ability to directly load an kernel and a mfsroot/initrd and pass
kernel loader arguments

set centos674_args edd=off ramdisk_size=50000 nomodeset
ksdevice=${net0/mac} verbose ip=dhcp
root-path=${centos-root}/CentOS6.7_x64/OS/ net.ifnames=0 biosdevname=0
echo ${centos674_args}
kernel ${base-root}/centos/CentOS6.7_x64/isolinux/vmlinuz ${centos674_args}
initrd ${base-root}/centos/CentOS6.7_x64/isolinux/initrd.img

> ...
> 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

mark saad | nonesuch at

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