NetBSD vs. Microkernels - From Kernel to Userspace and Abroad
A few weeks ago
I made a comment about NetBSD not being a "microkernel" despite
it's move to kernel modules. Antti Kantee wrote back to me (Hi Antti!)
reminding me of his work on RUMP, PUFFS and the like, which I think
does definitely deserve mentioning in that context:
With RUMP, PUFFS and the like, Antti is set on a mission to define
interfaces between kernel components, and move those kernel
components from inside the kernel to the userland. As a result,
the (once) kernel-code is now running as
processes that have all the benefits like memory protection
and not taking down the whole system in case of an error.
Examples that Antti has been bashing on started with
moving file systems to the userland, which resulted in PUFFS and
ReFUSE, an implementation of the Linux inferface of
File systems in USErland (FUSE). Not stopping at file systems
(which are traditionally used for accessing data on storage media,
like e.g. for ntfs-3g), Antti went further and moved into
getting network services like SSHFS going - in userland,
based on FUSE.
Not stopping there, more recent works include:
Remember when NetBSD got (re)FUSE? All of a sudden we got a
bazillion of filesystems back then. So why not turn this development around, and
make RUMP available as an interface for all sort of drivers
to other operating systems. That way, they can get our
file systems, usb stack and drivers, etc., and run them
in userspace as well. Developing a driver on one operating
system, and using it on many - a wet dream would come true!
Sounds impossible? Ye fear not, it's been done!
Arnaud 'stacktic' Ysmal already has ported RUMP to FreeBSD and Linux,
the work is available via
and there is also
Arnaud's page on
Rump on non-NetBSD Operating Systems for more information.
Whew... lots of research and development going on in this area,
and - getting back to the initial topic - we may well see an
operating system in the future that moves from the monolithic
to a microkernel approach, and it may or may not be called NetBSD.
Fact is, that a lot of research is going on in that area, on NetBSD,
here and now. Hats off, Antti!
[Tags: fuse, microkernel, nfs, ntfs-3f, puffs, refuse, rump, sshfs, tcp/ip, ukfs, usb]
Catching up - what happened in NetBSD-land between mid-August and mid-November
OK, I've been slacking^Wbusy for the past weeks, but I hope things
will get a bit better now. For a start, here's a catch-up of the
things that accumulated in my inbox in the past ~two months:
So much for today. With the NetBSD 5.0 release cycle started, I'd like
to encourage everyone to test the release branch, report errors, send
patches as well as beer and choccolate to make this the best
release that we've ever had.
- Google Summer of Code is over for some time, but apparantly
no final report has emerged so far (shame!). Still, a number
of individual status reports came by on the official lists:
I know of at least one other project (uvc) that has completed but
that I didn't see a report here - maybe I've missed it. Anyways,
GSoC was another big success this year. Thanks, Google!
- Speaking of Adam Hamsik and Logical Volume Management (LVM), Adam
has continued his work in that are, and he has written a device
mapping library that interacts with his kernel driver. This
allows to interact with his GSoC project without using any GPL
See Adam's posting for more details.
- Force 10 Networks, producer of 10gbit switches that use an operating system
based on NetBSD, have added a new feature as part of their FTOS operating
system: VirtualView, which provides virtualization of Force 10 based equipment.
From the xchange article: ``Force10 Networks Inc. this week introduced VirtualView software for benchmaking, troubleshooting and managing virtualized environments based on Force10 gear.''
More information is available
from the Force 10 Networks homepage,
plus in articles by
- Following the latest hype in portable computers, NetBSD has
created a netbook
page that intends to list models and the extent to which they
are supported. Your contributions are most welcome here! (Contact
me for sending updates and hardware :-)
- Zafer Aydogan has made RSS feeds available for CVS commits to
single files - see his mail to netbsd-users
for more details.
- New security advisory were released that I've missed in my
- A project that's been ongoing for quite some time is the move from
"old-school" loadable kernel modules (LKMs) to new-style kernel modules.
Important changes include the fact that modules can be either linked
into the kernel at build time, or loaded into the kernel at
runtime from the same file. Also, the bootloader was modified to
load modules after the kernel, e.g. for a RAM-disk like the one
that is used by the INSTALL kernel.
In the same line, some parts are starting to be moved out of the
GENERIC kernel, and installed as modules that can be loaded by
the new framework then. The start is made
POSIX semaphores as a first step and proof-of concept,
some details are still under hot debate, e.g.
what the file system layout for modules is, and if the belong
to the kernel and its build process, or to the userland.
- While talking about splitting the kernel into modules, Antti
Kantee has continued his work to move parts of the kernel into
userspace, in particular running file system code as userland in
and puffs and (Re)FUSE works.
The idea is to provide the interfaces that file systems need in
the userland, and the result is that you can run code that used
to run inside the kernel in userland now.
Another subsystem running in the kernel that could be moved to
userland by providing appropriate interfaces with the rest of the
kernel is the network stack, and Antti has moved just that to the
userland. See Antti's
mail to tech-net@ for more
information on this impressive work.
- NetBSD has shipped XFree in previous releases, and people who
wanted to use X.org had to install it from pkgsrc. That's all
fine, but to get a modern X, one had to compile things, as no
precompiled binary packages are made available for many
platforms. This is changing now, and NetBSD is getting X.org
integrated via a reachover infrastructure which is also enabled
The "user interface" for this is still in flux, but after some
detour ("build.sh -V MKXORG=yes", without -x), "build.sh -x" now
builds whatever X is considered the default for the
platform. Some platforms already default to use X.org as X, and
more will come, as changes that were made to NetBSD's copy of
XFree are adopted to X.org.
Platforms that use X.org by default now are macppc (see
amd64 and i386.
As X.org is at Revision 7 now, it's installed in /usr/X11R7,
which will lead to a lot of interesting effects. pkgsrc is
already prepared for the new layout, but there are still many
minor details that will need adjusting to the new directory. If
you find one, post your patches to tech-x11.
- Besides the GNU C compiler, there's the BSD-licensed Portable C Compiler
around for some time now. It doesn't offer the same support as
its GNU cousin yet, but this may change now:
The BSD Fund
is currently doing a fund drive to get money to enhance PCC.
The goal is to raise $12,000US to improve support for core
compiler functionality as well as support for C99, gcc
compatibility and the amd64 architecture. See
the project page for further details.
- The NetBSD 5.0 release cycle has started! There's a netbsd-5 branch in CVS,
daily binaries are available for testing, and some of
the highlights of the upcoming release include file system journalling for FFS via WAPBL, and X.org.
To help testing of NetBSD on Cobalt machines, Izumi Tsutsui
has made a NetBSD 5.0_BETA based version of the Cobalt restore CD
- As the final point today, a word on NUMA support from Christoph
Egger. Non-Uniform Memory Access is needed in massive parallel
systems where some nodes have RAM more tightly associated than
others, where the RAM is further away, resulting in different
access times for different regions of memory. In order to support
this, Christop Egger has made first steps.
His example implementation uses information from ACPI, and shows
some heavy dmesg-pr0n from a 16-core machine with four
[Tags: force10, fuse, gcc, google-soc, kmod, lkm, lvm, netbook, numa, pcc, puffs, refuse, rump, Security, x11, xfree, xorg]
Recent development related to puffs, ReFUSE, rump, and more (Updated)
NetBSD's kernel is under very active development these days, and
while many changes are related to improve SMP, it's not the only area.
An area where very interesting and unique work is being done is the
filesystem interfaces that Antti Kantee is working. Things started
out as a past year's Google "userfs" SoC project to implement an interface
for running filesystem code in userland. The project was imported
into NetBSD some time ago. On top of that, a library that mimics the
Linux interface for filesystems in userland. Following the Linux
name FUSE, the re-implementation is called ReFUSE (pun intended :).
webpage about puffs, refuse, FUSE
on the NetBSD website for more information.
Another project that was started by Antti after his work to
run filesystem code in userland is "rump". The project allows to use
"ordinary" filesystems that usually run inside the kernel, and
mimic an environment similar to what's available inside the kernel,
and move the whole filesystem into userland - verbatime, with
no code changes! This allows to develop filesystem code in userland,
and later on move it inside the kernel with no further changes - a
bit step forward for filesystem development!
This all sounds rather easy, but as filesystems need to move data between
storage and memory, a big issue in filesystems is interfacing with the
virtual memory subsystem, and adding interfaces like puffs and ReFUSE
also needs to consider VM for efficient transfers and caching.
Work in this area is still ongoing, and I've asked Antti about his
recent achievements in this area. While the only user-visible
change is caching and performance improvements in the Secure
Shell filesystem's handler "mount_psshfs", most of the changes
are on the inside. Antti wrote me:
``The interesting ones from a programmer's perspective are probably:
Finally, while not really useful for anything except puffs development,
I think the following is cool from the perspective of completeness:
rump, there are two very interesting and active projects
doing research in filesystems on NetBSD, which may lead to changes in
the way filesystems are understood in the Unix world. While there,
a third project that may be worth watching in this regards is
this year's Google
Summer of Code project by Marek Dopiera, which aims at
implementing Hurd translators for NetBSD,
Antti dropped me a note that another project related to
filesystems is this year's "fs-utils"
SoC project. The goal is to create a userland tool to manipulate filesystem
images, and the idea is to reuse kernel code with the
ukfs library. That way, no redundancy between kernel sources
and userland sources are created, and both areas benefit from mutual
testing and code maturity.
[Tags: filesystem, fuse, google-soc, kernel, puffs, refuse]
Mondo catch-up on source-changes (~Aug '07 'till Feb '08)
In the context of Mark Kirby
stopping his NetBSD CVS Digest,
I've felt an urge to catch up on
source-changes, and put
up some of the items here that I haven't found mentioned
or announced elsewhere (or that I've plainly missed)
after digging through some 7,000 mails. All those
available in NetBSD-current today
and that will be in NetBSD 5.0:
- Support C99 complex arithmetic was added by importing the
"cephes" math library
- POSIX Message queues were added
- bozohttpd was added as httpd.
- the x86 bootloader now reads /boot.cfg to configure banner
text, console device, timeout etc. - see boot.cfg(5)
- ifconfig(8) now has a "list scan" command to scan for access points
- SMP (multiprocessor) support is now enabled in i386 and amd64 GENERIC kernels
- Processor-sets, affinity and POSIX real-time extensions were added,
along with the schedctl(8) program to control scheduling of processes
- systrace was removed, due to security concerns
- the refuse-based Internet Access Node file system was committed, which
provides a filesystem interface to FTP and HTTP, similar to the old
alex file system,
- LKMs don't care for options MULTIPROCESSOR and LOCKDEBUG, i.e.
it's easier to reuse LKMs between debugging/SMP and non-debugging/SMP
- PCC, the Portable C Compiler that originates in the very beginnings of
Unix, was added to NetBSD. The idea is that it is used as alternative
to the GNU C Compiler in the long run.
- In addition to the iSCSI target (server) code that is already in
NetBSD 4.0, there'a also a refuse-based iSCSI initiator (client)
now, see http://mail-index.netbsd.org/source-changes/2007/11/08/0038.html
The above list is a mixed list of items. There are a number of
areas where there is very active development going on in NetBSD.
Andrew Doran is further working on SMP, fine-grained locking
inside the kernel and interrupt priority handling. Antti Kantee
has has done more work on his filesystems work (rump, puffs,
refuse/fuse), and Jared McNeill and Jörg Sonnenberger have
continued their work on NetBSD's power management framework.
Those changes are large and far-reaching, and I've yet to look
at them before I can report more here.
- Many driver updates and new drivers, see your nearest GENERIC kernel config file
- Many security updates, see list of security advisories
- Many 3rd software packages that NetBSD ships with were updated:
ipsec-tools (racoon), GCC 4.1, Automated Testing Framework 0.4,
OpenSSH 4.7, wpa_supplicant and hostapd 0.6.2, OpenPAM Hydrangea
So much on this subject for now. If someone's willing to help out
with continuing Mark Kirby's
NetBSD CVS Digest
either using his software-setup or by simply reading the list
and writing a monthly/weekly digest of the "interesting" changes,
I'd appreciate this very much. Put me on CC: for your postings! :)
[Tags: alex, bozohttpd, c99, cephes, cvs, cvs-digest, digest, ian, iscsi, lkm, pcc, refuse, smp, systrace]
Filesystems in User-Space: puffs, refuse vs. FUSE, and more (Updated)
[I'm taking the liberty to post this unquoted here, as I did the
editing on the news item, based on input from Antti
NetBSD now offers full support for running file systems in userspace.
The core component inside the kernel that exposes a file system
interface towards the userland programs is "puffs", and communicates
with vnodes, the kernel's own idea of files. The "libpuffs" library
is the interface between userland file systems and the kernel
component. To facilitate running the huge amount of file systems
already available for the FUSE interface, but not dictate the
capabilities of puffs by it, it was decided that FUSE support should
be provided as a compatibility layer on top of the native puffs
interface. This compatibility is offered by re-fuse, a BSD-licensed
re-implementation of FUSE. It is designed to be source code compatible
with FUSE, and more information can be found in the refuse(3) manpage.
While puffs is stable for users, the library programming interface and
the binary interfaces are still likely to change, and therefore puffs
and the dependant librefuse are not built by default. For people
tracking -current, the build of all relevant puffs components
(librefuse, psshfs, etc.) by "make build" can be enabled by adding
Using puffs also requires the kernel option "
file-system PUFFS", or alternatively loading the puffs.o kernel module,
which is included in a puffs-enabled build.
FUSE compatibility was added within pkgsrc, and besides the required
infrastructure work a number of FUSE packages were added to pkgsrc in the
new "filesystem" category. Example packages that are currently available
puffs was originally developed during the Google Summer of Code 2005
"userfs" project by Antti Kantee.
It was further polished using funding
from the Ulla Tuominen Foundation and committed
into the NetBSD source tree in October 2006.
The work was presented at AsiaBSDCon 2007 in a paper
entitled "puffs - Pass-to-Userspace Framework File System".
The "refuse" library was
written by Alistair Crooks and committed to NetBSD in February
2007. All components will be available in NetBSD releases starting
with NetBSD 5. Work for using FUSE-enabled packages via pkgsrc was
done by Juan Romero Pardines following import of the "refuse" library.
For more information, see NetBSD's webpage on file systems in userspace at
An in-depth technical description of puffs was presented at
in a paper entitled "puffs - Pass-to-Userspace Framework File System".
The paper and
[Tags: fuse, puffs, refuse]
Grab the RSS-feed,
or go back to my regular NetBSD page
Disclaimer: All opinion expressed here is purely my own.
No responsibility is taken for anything.