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@@ -660,3 +660,146 @@ Actually, the Hurd has never used an M:N model. Both libthreads (cthreads) and l
<braunr> but as youpi said, it still requires work
<braunr> and nobody's working on it
<braunr> you may want to check l4 fiasco.oc though
+
+
+# System Personality
+
+## IRC, freenode, #hurd, 2013-07-29
+
+ <teythoon> over the past few days I gained a new understanding of the Hurd
+ <braunr> teythoon: really ? :)
+ <tschwinge> teythoon: That it's a complex and distributed system? ;-)
+ <tschwinge> And at the same time a really simple one?
+ <tschwinge> ;-D
+ <teythoon> it's just a bunch of mach programs and some do communicate and
+ behave in a way a posix system would, but that is more a convention than
+ anything else
+ <teythoon> tschwinge: yes, kind of simple and complex :)
+ <braunr> the right terminology is "system personality"
+ <braunr> 11:03 < teythoon> over the past few days I gained a new
+ understanding of the Hurd
+ <braunr> teythoon: still no answer on that :)
+ <teythoon> braunr: ah, I spent lot's of time with the core servers and
+ early bootstrapping and now I gained the feeling that I've seen the Hurd
+ for what it really is for the first time
+
+
+# RPC Interfaces
+
+## IRC, freenode, #hurd, 2013-09-03
+
+ <rekado> I'm a little confused by the hurd and incubator git repos.
+ <rekado> DDE is only found in the dde branch in incubator, but not in the
+ hurd repo.
+ <rekado> Does this mean that DDE is not ready for master yet?
+ <braunr> yes
+ <rekado> If DDE is not yet used in the hurd (except in the dde branch in
+ the incubator repo), does pfinet use some custom glue code to use the
+ Linux drivers?
+ <braunr> this has nothing to do with pfinet
+ <braunr> pfinet is the networking stack, netdde are the networking drivers
+ <braunr> the interface between them doesn't change, whether drivers are in
+ kernel or not
+ <rekado> I see
+
+
+# IRC, freenode, #hurd, 2013-09-20
+
+ <giuscri> HI there, I have no previous knowledge about OS's. I'm trying to
+ undestand the structure of the Hurd and the comparison between, say,
+ Linux way of managing stuff ...
+ <giuscri> for instance, I read: "Unlike other popular kernel software, the
+ Hurd has an object-oriented structure that allows it to evolve without
+ compromising its design."
+ <giuscri> that means that while for adding feature to the Linux-kernel you
+ have to add some stuff `inside` a procedure, whilst in the Hurd kernel
+ you can just, in principle at least, add an object and making the kernel
+ using it?...
+ <giuscri> Am I making stuff too simple?
+ <giuscri> Thanks
+ <braunr> not exactly
+ <braunr> unix historically has a "file-oriented" structure
+ <braunr> the hurd allows servers to implement whatever type they want,
+ through the ability to create custom interfaces
+ <braunr> custom interfaces means custom calls, custom semantics, custom
+ methods on objects
+ <braunr> you're not restricted to the set of file interfaces (open, seek,
+ read, write, select, close, etc..) that unix normally provides
+ <giuscri> braunr: uhm ...some example?
+ <braunr> see processes for example
+ <braunr> see
+ http://darnassus.sceen.net/gitweb/savannah_mirror/hurd.git/tree/HEAD:/hurd
+ <braunr> this is the collection of interfaces the hurd provides
+ <braunr> most of them map to unix calls, because gnu aims at posix
+ compatibility too
+ <braunr> some are internal, like processes
+ <braunr> or authentication
+ <braunr> but most importantly, you're not restricted to that, you can add
+ your own interfaces
+ <braunr> on a unix, you'd need new system calls
+ <braunr> or worse, extending through the catch-all ioctl call
+ <giuscri> braunr: mhn ...sorry, not getting that.
+ <braunr> what part ?
+ <kilobug> ioctl has become such a mess :s
+ <giuscri> braunr: when you say that Unix is `file-oriented` you're
+ referring to the fact that sending/receiving data to/from the kernel is
+ designed like sending/receiving data to/from a file ...?
+ <braunr> not merely sending/receiving
+ <braunr> note how formatted your way of thinking is
+ <braunr> you directly think in terms of sending/receiving (i.e. read and
+ write)
+ <giuscri> braunr: (yes)
+ <braunr> that's why unix is file oriented, access to objects is done that
+ way
+ <braunr> on the hurd, the file interface is one interface
+ <braunr> there is nothing preventing you from implementing services with a
+ different interface
+ <braunr> as a real world example, people interested in low latency
+ profesionnal audio usually dislike send/recv
+ <braunr> see
+ http://lac.linuxaudio.org/2003/zkm/slides/paul_davis-jack/unix.html for
+ example
+ <kilobug> braunr: how big and messy ioctl has become is a good proof that
+ the Unix way, while powerful, does have its limits
+ <braunr> giuscri: keep in mind the main goal of the hurd is extensibility
+ without special privileges
+ <giuscri> braunr: privileges?
+ <braunr> root
+ <giuscri> braunr: what's wrong with privileges?
+ <braunr> they allow malicious/buggy stuff to happne
+ <braunr> and have dramatic effects
+ <giuscri> braunr: you're obviously *not* referring to the fact that once
+ one have the root privileges could change some critical-data
+ <giuscri> ?
+ <braunr> i'm referring to why privilege separation exists in the first
+ place
+ <braunr> if you have unprivileged users, that's because you don't want them
+ to mess things up
+ <braunr> on unix, extending the system requires privileges, giving those
+ who do it the ability to destroy everything
+ <giuscri> braunr: yes, I think the same
+ <braunr> the hurd is designed to allow unprivileged users to extend their
+ part of the system, and to some extent share that with other users
+ <braunr> although work still remains to completely achieve that
+ <giuscri> braunr: mhn ...that's the `server`-layer between the
+ single-application and kernel ?
+ <braunr> the multi-server based approach not only allows that, but
+ mitigates damage even when privileged servers misbehave
+ <braunr> one aspect of it yes
+ <braunr> but as i was just saying, even root servers can't mess things too
+ much
+ <braunr> for example, our old (sometimes buggy) networking stack can be
+ restarted when it behaves wrong
+ <braunr> the only side effect being some applications (ssh and exim come to
+ mind) which need to be restarted too because they don't expect the
+ network stack to be restarted
+ <giuscri> braunr: ...instead?
+ <braunr> ?
+ <kilobug> giuscri: on Linux, if the network stack crash/freezes, you don't
+ have any other option than rebooting the system - usually with a nice
+ "kernel pani"
+ <kilobug> giuscri: and you may even get filesystem corruption "for free" in
+ the bundle
+ <braunr> and hoping it didn't corrupt something important like file system
+ caches before being flushed
+ <giuscri> kilobug, braunr : mhn, ook