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[[!meta copyright="Copyright © 2011, 2012, 2013 Free Software Foundation,
Inc."]]
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[[!tag open_issue_documentation open_issue_hurd]]
# IRC, freenode, #hurd, 2011-08-10
< braunr> youpi: aren't sub-hurds actually called "neighbor hurds" ?
< youpi> no idea
< braunr> i also don't understand the recursive property
< youpi> a user can run a subhurd
< neal> braunr: What don't you understand?
< youpi> a user in a subhurd can run a subhurd
< youpi> etc
< braunr> i'm not sure it's really recursive
< neal> youpi: At some point it was observed that you don't strictly
require any resources from the "parent" Hurd.
< neal> youpi: i.e., you could have two Hurds running "directly" on Mach
< youpi> sure
< neal> youpi: Hence neighbor rather than sub
< youpi> but you need to be root for that
< youpi> or else your subhurd can't do much
< neal> you need to have been authorized to use the required resouces
< youpi> which is about the same :)
< neal> depends how they are delegated
< youpi> that's still asking root for something
< neal> if you say so
< youpi> which is most probably not the default
< braunr> well, either you depend on the parent to do things on your
behalf, or you directly have some privileged ports
< braunr> i'd agree with youpi that it's pretty much having root access at
some point
< youpi> and usually you don't have privileged ports by default :)
< braunr> but we don't need to restrict the presentation to user only sub
hurds
< braunr> people don't mind switching to root on their desktops
< braunr> which is one of the reasons they ask "what does the hurd really
bring me today ?"
< braunr> but being able to run truely separate hurds or recursive hurds is
something nice most OSes can't do easily
< youpi> switching to root becomes a *pain* when you have to do it 1 every
two commands
< braunr> yes sure, but some people might just say you're clumsy :x
< neal> The question is: can I start a sub-hurd from within another hurd
that survives the parent's hurd exiting? The answer is yes. The reason
is that the sub-hurd can be constructed in such a way that it does not
rely on the parent. In this case, the parent does not necessarily
subjugate the sub-hurd. Hence the name.
< braunr> but that's out of the scope of the discussion
< antrik> using the traditional, root only mechanism, neighbour-hurd is
indeed a more appropriate term. apart from the initial terminal being
proxied to the parent system by the boot program, they are really equal
< antrik> with zhengda's work on non-root subhurds, you rely on various
proxies in the parent system to access privileged resources; so subhurd
is indeed a more appropriate term in this case
< antrik> (not only non-root subhurds in fact... when using any of the
proxies, such as the network multiplexer -- even if still running as
root...)
< youpi> antrik: you could still give a com0 port as terminal
< antrik> I don't think that's actually supported in the boot
program... but it doesn't really matter, as you don't really need the
terminal anyways -- you can always log in through the network
# IRC, freenode, #hurd, 2012-07-31
<gg0> subhurd seems like bsd jail (tried none of them)
<antrik> gg0: nope. BSD jails are mostly chroot AIUI. subhurd is quite
different
<antrik> gg0: you actually boot a completely new system instance
<antrik> complete with all the Hurd servers, UNIX daemons etc.
<braunr> jails are between subhhurds and chroots :p
<braunr> i suppose there is nothing against making the root server of the
subhurd use a file instead of a raw disk, is there ?
<gg0> well, I said jails cos afaik are more isolated from real system than
chroots
<braunr> yes
<gg0> maybe comparing subhurd to virtual machines would be more
appropriated then
<braunr> they're not VMs either
<gg0> say chroot -> jail -> subhurd -> vm ?
<braunr> unless you consider the microkernel to be a hypervisor, with its
own architecture, which some actually do
<braunr> gg0: something like that, yes
<gg0> [system-in-system evolution]
<braunr> a subhurd is an operating system instance
<braunr> i think the closest analogy you can get is openvz
<antrik> yeah, I'd also consider it closest. but it's still quite
different: with OpenVZ, the kernel facilities are only logically
isolated; but they use the same kernel code. with subhurds, most of the
system facilities are independent
# IRC, freenode, #hurd, 2012-08-03
<antrik> hm... are Mach task IDs exposed to userspace?
<braunr> antrik: ids ?
<braunr> antrik: what do you call a mach task id ?
<antrik> task have numeric IDs in the kernel
<antrik> I wonder whether these are ever exposed to userspace
<braunr> i'm not sure
<braunr> i don't remember the had numeric IDs
<braunr> they*
<antrik> well, perhaps I'm making things up... but I believe I saw such IDs
in the debugger and/or in error messages
<braunr> probably their address
<braunr> or creation time orpc_sample
<antrik> braunr: well, any unique ID would do
<braunr> antrik: yes but i was wondering what kdb would actually show
<antrik> I just realised that it would be useful for debugging accross
subhurds or kernel/userspace if some kind of unique task IDs could be
shown in ps output
<braunr> yes
<braunr> this requires some thought though
<braunr> ps shouldn't show that
<braunr> there should be mach specific commands i suppose
<braunr> but then, gdb and other tools wouldn't have access to subhurd
tasks either
<antrik> why shouldn't ps show that? I don't think it's any more sensitive
information than all the other stuff ps shows...
<braunr> it doesn't feel right
<braunr> i would want my system instances to be truely isolated
<braunr> and use special "cross instance" facilities
<braunr> when necessary
<antrik> that's completely orthogonal to what I'm talking about
<braunr> like eth-multiplexer
<braunr> you seem to be talking about security
<braunr> or privacy
<antrik> we discussed such options when zhengda worked on rootless subhurd
<antrik> no, I'm talking about convenient debugging
<braunr> right
<braunr> i don't think it'zs orthogonal here
<braunr> if we increase separation, it becomes less convenient
<antrik> for debugging purposes you would *not* use the isolation options
<braunr> ok so you propose two modes of operations
<antrik> BTW, as an isolated subhurd relies on the parent, it makes no
sense to hide subhurd tasks from the parent hurd -- only hide parent hurd
task from the subhurd
<braunr> agreed
<antrik> so even with an isolated subhurd global task IDs would still be
useful
# IRC, freenode, #hurd, 2012-08-06
<braunr> antrik: if i'm right, the root file system executable is read from
the parent, right ?
<antrik> braunr: probably... I'm not sure about that part
<braunr> antrik: i've installed the same packages in both the main and
subhurds to be sure
<braunr> and to have the right binary and debugging symbols in gdb anyway
# IRC, freenode, #hurd, 2013-01-19
<zacts> what is the hurd equivalent of a freebsd jail?
<braunr> zacts: i'd say subhurds
<zacts> what advantages would a subhurd have over a freebsd jail?
<zacts> basically that is
<braunr> it virtually guarantees a mistake can't compromise the main system
<zacts> ah ok
<braunr> in theory, subhurds can run without root privileges
<braunr> (but there are currently a few things that prevent it)
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