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[[!tag open_issue_documentation]]
It is possible to run Hurd stuff on top of another system instead of on Mach.
One obvious variant is emulation ([[hurd/running/QEMU]], for example), but
doing that does not really integratable the Hurd guest into the host system.
There is also a more direct way, more powerful, but it also has certain
requirements to do it effectively:
IRC, #hurd, August / September 2010
<marcusb> silver_hook: the Hurd can also refer to the interfaces of the
filesystems etc, and a lot of that is really just server/client APIs that
could be implemented on any system that has transferable rights to message
capabilities.
<marcusb> silver_hook: it's surprising how few systems *have* transferable
rights, though!
<marcusb> silver_hook: usually it is added as an afterthought
<marcusb> and comes with restriction
<youpi> marcusb: there's SCM_RIGHTS to transfer fds, which is quite often
available
<marcusb> youpi: yes, I know this as "fdpassing"
<marcusb> youpi: it's described in the Stevens series even
[...]
<marcusb> ArneBab: well, let me put it this way. the Linux kernel has no
interface to manipulate another tasks's virtual address space, ie you can't
map/unmap stuff in another process
<marcusb> ArneBab: you would have to use ptrace and load some stub code in that
process to make that happen.
<marcusb> ArneBab: so for complete transparent manipulation, you need a kernel
module
<marcusb> that is what the User Mode Linux kernel module does
<marcusb> ArneBab: so say you use the User Mode Linux kernel module for that
one feature. Then you can do everything that User Mode Linux can do, which,
I assure you, includes running subhurds :)
<marcusb> it can be a bit tricky to implement those features, but it is not
harder than writing a kernel in the first place
<ArneBab> So, if I got an admin to install User Mode Linux and Mach emulation,
I’d get the flexibility (and independence from admin decisions) I have in the
Hurd?
<marcusb> ArneBab: one problem is that you still use Linux. For those who want
to get rid of Linux for political reasons, that would mean complete failure
<marcusb> ArneBab: if you have UML kernel module, you can implement Mach in
user space
<marcusb> ArneBab: in fact, John Tobey did this a couple of years ago, or
started it
([[tschwinge]] has tarballs of John's work.)
<marcusb> ArneBab: or you can just implement parts of it and relay to Linux for
the rest
<marcusb> the point is, that if you don't care for kernel improvements, and are
sufficiently happy with the translator stuff, it's not hard to bring the Hurd
to Linux or BSD
(Continue: [[benefits]].)
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