A lot has happened with respect to the Hurd
since our Childhurds and GNU/Hurd
Substitutes
post. As long as two years ago some of you have been
asking for a
progress update and although there have been
rumours
on a new blog post for over a year, we
were kind of
waiting for
the rumoured x86_64
support.

With all the exciting progress on the Hurd coming available after the
recent (last?) merger of
core-updates
we thought it better not to
wait any
longer. So here is a short overview of our Hurd work over the past
years:

• Update Hurd to 3ff7053, gnumach 1.8+git20220827, and fix build
  failures,

• A native compilation fix for
  gcc-boot0,

• Initial rumpdisk
  support,
  more on this below, which needed to
  wait
  for:

• A libc specific to
  Hurd,
  updating gnumach to 1.8+git20221224 and hurd to 0.9.git20230216,

• Some 40 native package build fixes for the
  Hurd
  so that all development dependencies of the guix package are now
  available,

• A hack to use Git source in commencement to update and fix cross
  build and native build for the
  Hurd,

• Support for buiding guix natively on the Hurd by splitting the
  build into more steps for 32-bit
  hosts

• Even nicer offloading support for Childhurds by introducing Smart
  Hurdloading
  so that now both the Bordeaux and Berlin build farms build
  packages for i586-gnu,

• Locale fixes for wrong glibc-utf8-locales package used on
  GNU/Hurd,

• More locale fixes to use glibc-utf8-locales/hurd in
  %standard-patch-inputs,

• And even more locale fixes for using the right locales on
  GNU/Hurd,

• A new glibc
  2.38
  allowing us to do (define-public glibc/hurd glibc)—i.e., once
  again use the same glibc for Linux and Hurd alike, and: Better
  Hurd support!,

• Creation of hurd-team
  branch
  with build fixes, updating gnumach to 1.8+git20230410 and hurd to
  0.9.git20231217,

• A constructive meeting with sixteen people during the Guix
  Days
  just before FOSDEM ’24 with
  notes
  that contain some nice ideas,

• Another new glibc
  2.39;
  even better Hurd support, opening the door to x86_64 support,

• Yet another restoring of i586-gnu (32-bit GNU/Hurd)
  support,

• The installer just learnt about the
  Hurd!
  More on this below, and finally,

• Another set of updates: gnumach (1.8+git20240714), mig
  (1.8+git20231217), hurd (0.9.git20240714), netdde (c0ef248d),
  rumpkernel (f1ffd640), and initial support for x86_64-gnu, aka
  the 64bit
  Hurd.

NetDDE and Rumpdisk support

Back in 2020, Ricardo Wurmus added the NetDDE
package
that provides Linux 2.6 network drivers. At the time we didn’t get to
integrate and use it though and meanwhile it bitrotted.

After we resurrected the NetDDE
build,
and with kind help of the Hurd
developers
we finally managed to support NetDDE for the
Hurd..
This allows the usage of the Intel 82573L Gigabit Ethernet Controller
of the Thinkpad X60 (and many other network cards, possibly even
WIFI). Instead of using the builtin kernel driver in GNU Mach, it
would be running as a userland driver.

What sparked this development was upstream’s NetBSD rumpdisk support
that would allow using modern hard disks such as SSDs, again running
as a userland driver. Hard disk support builtin in GNU Mach was
once considered to be a nice hack but it only supported disks up to
128 GiB…

First, we needed to fix the cross build on
Guix.

After the initial attempt at rumpdisk support for the
Hurd
it took
(v2)
some
(v3)
work
(v4)
to finally arrive at rumpdisk support for the Hurd, really, *really*
(v5)

Sadly when actually using them, booting hangs:

start: pci.arbiter:

What did not really help is that upstream’s rumpkernel archive was
ridiculously
large.
We managed to work with upstream to remove unused bits from the
archive. Upstream created a new archive that instead of 1.8 GiB (!) now
“only” weighs 670 MiB.

Anyway, after a lot of building, rebuilding, and debugging and some
more with kind help from
upstream
we finally got Rumpdisk and NetDDE to run in a
Childhurd.

Initial Guix/Hurd on the Thinkpad X60

Now that the last (!) core-updates merge has finally happened (thanks
everyone!), the recipe of installing Guix/Hurd has been much
simpfilied. It goes something along these lines.

1. Install Guix/Linux on your X60,

2. Reserve a partition and format it for the Hurd:

   mke2fs -o hurd -L hurd /dev/sdaX

3. In your config.scm, add some code to add GRUB menuentries for
   booting the Hurd, and mount the Hurd partition under /hurd:

   (use-modules (srfi srfi-26)
                (ice-9 match)
                (ice-9 rdelim)
                (ice-9 regex)
                (gnu build file-systems))
   
   (define %hurd-menuentry-regex
     "menuentry "(GNU with the Hurd[^{"]*)".*multiboot ([^ n]*) +([^n]*)")
   (define (text->hurd-menuentry text)
     (let* ((m (string-match %hurd-menuentry-regex text))
            (label (match:substring m 1))
            (kernel (match:substring m 2))
            (arguments (match:substring m 3))
            (arguments (string-split arguments #space))
            (root (find (cute string-prefix? "root=" <>) arguments))
            (device-spec (match (string-split root #=)
                           (("root" device) device)))
            (device (hurd-device-name->device-name device-spec))
            (modules (list-matches "module ([^n]*)" text))
            (modules (map (cute match:substring <> 1) modules))
            (modules (map (cute string-split <> #space) modules)))
       (menu-entry
        (label label)
        (device device)
        (multiboot-kernel kernel)
        (multiboot-arguments arguments)
        (multiboot-modules modules))))
   
   (define %hurd-menuentries-regex
     "menuentry "(GNU with the Hurd[^{"]*)" \{([^}]|[^n]\})*n\}")
   (define (grub.cfg->hurd-menuentries grub.cfg)
     (let* ((entries (list-matches %hurd-menuentries-regex grub.cfg))
            (entries (map (cute match:substring <> 0) entries)))
       (map text->hurd-menuentry entries)))
   
   (define (hurd-menuentries)
     (let ((grub.cfg (with-input-from-file "/hurd/boot/grub/grub.cfg"
                       read-string)))
       (grub.cfg->hurd-menuentries grub.cfg)))
   
   ...
   (operating-system
      ...
     (bootloader (bootloader-configuration
                  (bootloader grub-bootloader)
                  (targets '("/dev/sda"))
                  (menu-entries (hurd-menuentries))))
     (file-systems (cons* (file-system
                            (device (file-system-label "guix"))
                            (mount-point "/")
                            (type "ext4"))
                          (file-system
                            (device (file-system-label "hurd"))
                            (mount-point "/hurd")
                            (type "ext2"))
                          %base-file-systems))
     ...)

4. Create a config.scm for your Hurd system. You can get
   inspiration from bare-hurd.tmpl
   and inherit from %hurd-default-operating-system. Use
   grub-minimal-bootloader and add a static-networking-service-type.
   Something like:

   (use-modules (srfi srfi-1) (ice-9 match))
   (use-modules (gnu) (gnu system hurd))
   
   (operating-system
     (inherit %hurd-default-operating-system)
     (bootloader (bootloader-configuration
                  (bootloader grub-minimal-bootloader)
                  (targets '("/dev/sda"))))
     (kernel-arguments '("noide"))
   ...
     (services
       (cons*
         (service static-networking-service-type
                  (list %loopback-static-networking
                        (static-networking
                         (addresses
                          (list
                           (network-address
                            (device "eth0")
                            (value "192.168.178.37/24"))))
                         (routes
                          (list (network-route
                                 (destination "default")
                                 (gateway "192.168.178.1"))))
                         (requirement '())
                         (provision '(networking))
                         (name-servers '("192.168.178.1")))))
       ...)))

5. Install the Hurd. Assuming you have an ext2 filesystem mounted
   on /hurd, do something like:

   guix system build --target=i586-pc-gnu vuurvlieg.hurd --verbosity=1
   sudo -E guix system init --target=i586-pc-gnu --skip-checks 
       vuurvlieg.hurd /hurd
   sudo -E guix system reconfigure vuurvlieg.scm

6. Reboot and…

Hurray!

We now have Guix/Hurd running on
Thinkpad.

Guix/Hurd on Real Iron

While the initial manual install on the X60 was an inspiring
milestone, we can do better. As mentioned above, just recently the
installer learnt about the
Hurd,
right after some smaller problems were addressed, like guix system init creating essential devices for the Hurd, not attempting to run a
cross-built grub-install to install Grub, soft-coding the hard-coded
part:1:device:wd0 root file-system, adding support for booting
Guix/Hurd more than once.

To install Guix/Hurd, first, build a 32bit installation image and copy
it to a USB stick:

guix system image --image-type=iso9660 --system=i686-linux gnu/system/install.scm
dd if=/gnu/store/cabba9e-image.iso of=/dev/sdX status=progress
sync

then boot it on a not-too-new machine that has wired internet
(although installation over WIFI is possible, there is currently no
WIFI support for the installed Hurd to use it). On the new Kernel
page:

choose Hurd. Do not choose a desktop environment, that’s not
available yet. On the Network management page:

choose the new Static networking service. In the final
Configuration file step, don’t forget to edit:

and fill-in your IP and GATEWAY:

You may want to add some additional packages such as git-minimal
from (gnu packages version-control) and sqlite from (gnu packages sqlite).

If you also intend to do Guix development on the Hurd—e.g., debugging
and fixing native package builds—then you might want to include all
dependencies to build the guix package, see the
devel-hurd.tmpl
for inspiration on how to do that. Note that any package you add must
already have support for cross-building.

Good luck, and let us know if it works for you and on what kind of
machine, or why it didn’t!

What’s next?

In an earlier
post
we tried to answer the question “Why bother with the Hurd anyway?” An
obvious question because it is all too easy to get
discouraged, to downplay or underestimate the
potential social impact of GNU and the Hurd.

The most pressing problem currently is that the guix-daemon fails
when invoking guix authenticate on the
Hurd, which means that we cannot
easily keep our substitutes up to date. guix pull is known to work
but only by pulling from a local branch doing something like:

mkdir -p ~/src/guix
cd src/guix
git clone https://git.savannah.gnu.org/git/guix.git master
guix pull --url=~/src/guix/master

kinda like we did it in the old days. Sometimes it seems that guix
does not grok the sqlite store database. This is needs to be resolved
but as sqlite does read it this can be easily worked around by doing
something like:

mv /var/guix/db/db.sqlite /var/guix/db/db.sqlite.orig
sqlite3 /var/guix/db/db.sqlite.orig .dump > /var/guix/db/db.sqlite.dump
sqlite3 -init /var/guix/db/db.sqlite.dump /var/guix/db/db.sqlite .quit

Also, the boot process still fails to handle an unclean root file
system. Whenever the Hurd has suffered an unclean shutdown, cleaning
it must currently be done manually, e.g., by booting from the
installer USB stick.

Upstream now has decent support for 64bit (x86_64) albeit with more
bugs and fewer
packages.
As mentioned in the overview we are now
working
to have
that
in
Guix
and have
made
some progress:

more on that in another post. Other interesting task for Guix
include:

• Have guix system reconfigure work on the Hurd,
• Figure out WiFi support with NetDDE (and add it to installer!),
• An isolated build
  environment (or better
  wait for, err, contribute to the Guile
  guix-daemon?),
• An installer running the Hurd, and,
• Packages, packages, packages!

We tried to make Hurd development as easy and as pleasant as we could.
As you have seen, things start to work pretty nicely and there is
still plenty of work to do in Guix. In a way this is “merely
packaging” the amazing work of others. Some of the real work that
needs to be done and which is being discussed and is in progress right
now includes:

• Audio support (this is
  sponsored by NLnet, thanks!),
• Rumpnet,
• SMP,
• AArch64.

All these tasks look daunting, and indeed that’s a lot of work ahead.
But the development environment is certainly an advantage. Take an
example: surely anyone who’s hacked on device drivers or file systems
before would have loved to be able to GDB into the code, restart it, add
breakpoints and so on—that’s exactly the experience that the Hurd
offers. As for Guix, it will make it easy to test changes to the
micro-kernel and to the Hurd servers, and that too has the potential to
speed up development and make it a very nice experience.

Join #guix and #hurd on
libera.chat or the mailing
lists and get involved!