branch master updated: website: drafts: Add draft post on substitutes for the Hurd.

[Jan Nieuwenhuizen]

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     new 3c9aceb  website: drafts: Add draft post on substitutes for the Hurd.
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commit 3c9aceb70067a5fcd9804afd585c9b28085ad57f
Author: Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
AuthorDate: Sat Oct 3 15:40:34 2020 +0200

    website: drafts: Add draft post on substitutes for the Hurd.
    
    * website/posts/childhurds-and-substitutes.md,
    website/static/blog/img/hurd-substitutes.gif: New files.
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+title: DRAFT Childhurds and GNU/Hurd substitutes
+date: 2020-10-07 00:00
+author: Jan (janneke) Nieuwenhuizen, Ludovic Courtès, Mathieu Othacehe
+slug: childhurds-and-substitutes
+tags: GNU/Hurd
+---
+
+A lot has happened since our [Hello Hurd
+post](https://guix.gnu.org/blog/2020/hello-hurd/) beginning of April.
+No, not nearly as much as [we joked on April 1st
+](https://guix.gnu.org/blog/2020/deprecating-support-for-the-linux-kernel/),
+but more than enough to share and be proud of.
+
+# Building a Hurd virtual machine
+
+As some of you noticed, the previous hacks to build a Hurd virtual
+machine (VM) were
+removed and no longer work; using Guix you can now build a GNU/Hurd VM
+just like you would build a GNU/Linux VM:
+
+```
+guix system disk-image --target=i586-pc-gnu bare-hurd.tmpl
+```
+
+This cross-compiles all the relevant packages for GNU/Hurd—specifically the
+`i586-pc-gnu`
+[triplet](https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Specifying-Target-Triplets.html)—and
 produces a VM image:
+
+```
+/gnu/store/n7jkfajw0fzp975hv0b9v18r9bbr961q-disk-image
+```
+
+You can build it and start it from your GNU/Linux machine with this
+command:
+
+```
+qemu-system-i386 -enable-kvm -m 512 -snapshot -hda \
+  $(guix system disk-image --target=i586-pc-gnu bare-hurd.tmpl)
+```
+
+We are using this ready-made, minimal GNU/Hurd operating system
+description
+[gnu/system/examples/bare-hurd.tmpl](https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/examples/bare-hurd.tmpl)
+that looks suprisingly familiar:
+
+```scheme
+(use-modules (gnu) (gnu system hurd) (guix utils))
+(use-service-modules ssh)
+(use-package-modules ssh)
+
+(define %hurd-os
+  (operating-system
+    (inherit %hurd-default-operating-system)
+    (bootloader (bootloader-configuration
+                 (bootloader grub-minimal-bootloader)
+                 (target "/dev/sdX")))
+    (file-systems (cons (file-system
+                          (device (file-system-label "my-root"))
+                          (mount-point "/")
+                          (type "ext2"))
+                        %base-file-systems))
+    (host-name "guixygnu")
+    (timezone "Europe/Amsterdam")
+    (packages (cons openssh-sans-x %base-packages/hurd))
+    (services (cons (service openssh-service-type
+                             (openssh-configuration
+                              (openssh openssh-sans-x)
+                              (use-pam? #f)
+                              (port-number 2222)
+                              (permit-root-login #t)
+                              (allow-empty-passwords? #t)
+                              (password-authentication? #t)))
+               %base-services/hurd))))
+
+%hurd-os
+```
+
+and it can be customized just like a GNU/Linux operating system
+description.  The end result is a full-blown Guix System with [the
+Shepherd](https://gnu.org/software/shepherd) managing system services
+and all that—finally we can run
+[`herd`](https://www.gnu.org/software/shepherd/manual/html_node/Invoking-herd.html)
+on the Hurd.
+
+A lot of things had to be in place to support this, we worked on
+
+ * Adding [Multiboot support](https://en.wikipedia.org/wiki/Multi-booting)
+   to 
[grub-minimal-bootloader](https://git.savannah.gnu.org/cgit/guix.git/?commit=1244491a0d5334e1589159a2ff67bbc967b9648b);
 a nice standard that Linux sadly does
+   not support,
+ * Support for the Hurd and cross-building of
+      
[%base-packages/hurd](https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/hurd.scm#n62),
+ * Support for the hurd and cross-building of
+    
[%base-services/hurd](https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/hurd.scm#n67),
+   - Add 
[hurd-console-service](https://git.savannah.gnu.org/cgit/guix.git/?commit=f9c04580bf5462bb088f47ad8fc6c3136649cbd6),
+   - Add 
[hurd-getty-service](https://git.savannah.gnu.org/cgit/guix.git/?commit=7ccd471c71d650055e99cd02381bc8dcd86d5313),
+   - Add 
[hurd-default-essential-services](https://git.savannah.gnu.org/cgit/guix.git/?commit=45b2cb439deaa2f438aed3893ee8fc80445d5563),
+   - Add Hurd support to the 
[%boot-service](https://git.savannah.gnu.org/cgit/guix.git/?commit=b37c544196898cc3dfa3da07ed344fbe11abc120)
+   - Add a 
[hurd-startup-service](https://git.savannah.gnu.org/cgit/guix.git/?commit=68d8c094659565fe19abc1c433a17337ce5cacb7),
+   - Add Hurd support to the 
[activation-service](https://git.savannah.gnu.org/cgit/guix.git/?commit=c3fd2df705695a0dc9f393545606360be1ea6104),
+
+counting some ~200 patches by ten people over six months; including
+generic cross-compilation fixes and support, and Hurd fixes and
+support.
+
+Also, we finished the passive translator settings over extended
+attributes (_xattrs_) [for the
+Hurd](https://git.savannah.gnu.org/cgit/hurd/hurd.git/commit/?id=a04c7bf83172faa7cb080fbe3b6c04a8415ca645)
+and [for
+Linux](https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=88ee9d571b6d8ed345f877e05f685814412e359b).
+
+You may notice that we are using the new `disk-image` command rather
+than the old `vm-image`.  One of the big hurdles in producing a
+VM image was the way Guix produces VM images: it would run a GNU/Linux
+system in QEMU to initialize the image.  Without going into the hairy
+details, when Ludo and Janneke were almost ready to give up, Matthieu
+came to the rescue with his brand-new implementation of the
+`disk-image` command.  At the time, Hurd work was done on the
+`wip-hurd` branch and the disk-image work on `wip-disk-image`.  Soon
+after, Mattieu proposed an "explosive mix" of the two branches, we
+managed to create the first Hurd system that really felt like Guix System.
+
+XXX TODO: on the goodies of --image-type, qcow2-hurd
+
+We also offer downloads of continuously built (actually cross-built)
+[Guix System on
+GNU/Hurd](https://ci.guix.gnu.org/search/latest/image?query=spec:guix-master+status:success+system:x86_64-linux+hurd-barebones.qcow2)
+(~350 MiB).
+
+# Substitutes
+
+While amazing to be able to just run the Hurd in a VM, development without
+[substitutes](https://guix.gnu.org/manual/en/html_node/Substitutes.html)
+is a real pain; a Guix system needs substitutes.  How to
+go about that?  We have a build farm but currently Hurd only runs on
+ancient hardware: not an option.  We need a machine running Guix/Hurd
+to
+[offload](https://guix.gnu.org/manual/devel/en/html_node/Daemon-Offload-Setup.html)
+Hurd build jobs to.
+
+The proposed solution was to automate the building and running of a
+Guix VM into a new Guix service: the so-called `hurd-vm` or `childhurd`
+service.  We would add something like:
+
+```scheme
+(service hurd-vm-service-type)
+```
+
+to a couple of our build nodes to add a hird of virtual Hurd machines
+to our build farm.
+
+# The Childhurd service
+
+The Hurd—being based on a microkernel—has some beautiful built-in
+"virtualization" possibilites that have their own naming:
+[neighborhurd](https://www.gnu.org/software/hurd/hurd/neighborhurd.html)s,
+[subhurd](https://www.gnu.org/software/hurd/hurd/subhurd.html)s.
+Similarly, we are adding
+[_childhurds_](https://guix.gnu.org/development/manual/en/html_node/Virtualization-Services.html#Childhurd)
+to this mix: a childhurd is a GNU/Hurd VM running on GNU/Linux and
+managed by Guix.
+
+When you are running Guix System, building a Hurd VM manually is no
+longer necessary.  Just add [the `hurd-vm`
+service](https://guix.gnu.org/manual/devel/en/html_node/Transparent-Emulation-with-QEMU.html#The-Hurd-in-a-Virtual-Machine)
+to your operating
+system description:
+
+```scheme
+(service hurd-vm-service-type
+         (hurd-vm-configuration
+          (* 12 (expt 2 30))      ;12GiB
+          (memory-size 1024)))    ; 1GiB
+```
+
+and this will build a childhurd for you when you reconfigure your
+system.  This childhurd can be stopped and started just like any other
+service:
+
+```bash
+herd stop hurd-vm
+herd start childhurd
+```
+(`childhurd` is an alias for `hurd-vm`).
+
+*WARNING*
+
+![This Hurd is fully 
operational](https://guix.gnu.org/static/blog/img/hurd-substitutes.gif)
+
+It is highly addictive.
+
+Having shaved this yak, let’s not use sight that our initial goal was to
+offload builds to those GNU/Hurd VMs.  The childhurd service does all
+the heavy lifting.  To offload from GNU/Linux to my childhurd, I added
+this to my `/etc/guix/machines.scm`:
+
+```
+ (build-machine
+  (name "localhost")
+  (systems (list "i586-gnu"))
+  (host-key "ssh-ed25519 
AAAAC3NzaC1lZDI1NTE5AAAAIHZsrZ63zs+AhWbVJgYq6j1h2rgQGrWKCokpR2/Q/Jzy 
root@guixygnu")
+  (port 10022)  ;the Hurd VM has SSH listening on that port
+  (user "root")
+  (private-key "/home/janneke/.ssh/id_rsa_childhurd"))
+```
+
+That can be used to transparently offload builds from GNU/Linux to the
+childhurd:
+
+```bash
+$ uname -o
+GNU/Linux
+$ guix build hello -s i586-gnu
+The following derivation will be built:
+   /gnu/store/jqdvjhcxxnbq370y8i2c973c9zfiqrgl-hello-2.10.drv
+[…]
+guix offload: sending 1 store item (12 MiB) to 'localhost'...
+offloading '/gnu/store/jqdvjhcxxnbq370y8i2c973c9zfiqrgl-hello-2.10.drv' to 
'localhost'...
+[…]
+/gnu/store/803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10
+$ file -L $(guix build hello -s i586-gnu)/bin/hello
+/gnu/store/803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10/bin/hello: ELF 32-bit 
LSB executable, Intel 80386, version 1 (SYSV), dynamically linked, interpreter 
/gnu/store/9vs3gkp6svam82zw7vjlml7iiarcs11c-glibc-2.31/lib/ld.so.1, for 
GNU/Hurd 0.0.0, not stripped
+```
+
+Hurrah!
+
+# Hurd substitutes
+
+The very first [GNU Hello
+substitute](https://ci.guix.gnu.org/803q5wapfnmr91ag8d9dzwabkbdxz3ay.narinfo)
+for the Hurd, which looks like this:
+
+```
+StorePath: /gnu/store/803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10
+URL: nar/gzip/803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10
+Compression: gzip
+FileSize: 61822
+URL: nar/lzip/803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10
+Compression: lzip
+FileSize: 52887
+NarHash: sha256:0g4k1kppjs5148ynm4zw4x1kpaby67npc3ws6s7y7hf0il1cgryk
+NarSize: 204328
+References: 803q5wapfnmr91ag8d9dzwabkbdxz3ay-hello-2.10 
9vs3gkp6svam82zw7vjlml7iiarcs11c-glibc-2.31 
bwvd5338kfm0vsc4i9xvh48vdxr5ywrz-gcc-7.5.0-lib
+System: i586-gnu
+Deriver: jqdvjhcxxnbq370y8i2c973c9zfiqrgl-hello-2.10.drv
+Signature: 
1;berlin.guix.gnu.org;KHNpZ25hdHVyZSAKIChkYXRhIAogIChmbGFncyByZmM2OTc5KQogIChoYXNoIHNoYTI1NiAjMDVGOEY5NjMxRUU5QzcxM0REQUNBRTYwNUNCNjJBNzlDNUY4NEVFQTIwMjc5OERBNTQ3NURCOUU2Q0FBRDMwMSMpCiAgKQogKHNpZy12YWwgCiAgKGVjZHNhIAogICAociAjMDVBMzkzMTgwOUY1RkQyMTdGMDM4MUVDMTJEODYyNzIyOEYyNjJGRDA4MTcxQjREMzZBNEM0RjBBNjZEQkY4NSMpCiAgIChzICMwQTc2RjZGNENCOTMzQTczNzA4QkNGMzRGREExMzkyOTRGQTQxREQzQTUwQkEwOUE0ODRCQUQyOTA4MjQ5ODIxIykKICAgKQogICkKIChwdWJsaWMta2V5IAogIChlY2MgCiAgIChjdXJ2ZSBFZDI1NTE5KQo
 [...]
+```
+
+Any day now, more [Hurd
+substitutes](https://ci.guix.gnu.org/jobset/hurd-hello) will follow.
+
+
+XXX: "It works"...but maybe "wait" until we have substitutes to support this? 
XXX
+
+For development, I am using something like this
+
+```scheme
+(use-modules (srfi srfi-1) (guix packages) (guix records))
+(use-package-modules base compression file gawk gdb hurd less m4 
package-management)
+
+(define guix-packages
+  (filter-map input->package
+              (fold alist-delete (package-direct-inputs guix)
+                    '("glibc-utf8-locales" "graphviz" "po4a"))))
+
+(operating-system
+  (inherit %hurd-vm-operating-system)
+  (users ...)
+  (packages
+    (cons* diffutils file findutils gawk gdb-minimal git-minimal
+           gnu-make grep gzip less m4 openssh-sans-x tar xz
+           (append
+            guix-packages
+            (delete guile-3.0 %base-packages/hurd)))))
+```
+
+… which allows working from a Git clone:
+
+```bash
+15:51:05 janneke@dundal:~/src/guix/master [env]
+$ ssh -A janneke@childhurd
+Last login: Sat Oct  3 15:31:55 2020 from 10.0.2.2
+
+
+  This is the GNU Hurd.  Welcome.
+
+janneke@childhurd ~$ guix environment guix
+The following derivations will be built:
+   /gnu/store/76dv7icw720jzxdylfdaphv6x09m6q93-libx11-1.6.A.drv
+   /gnu/store/1nmm09wksvvln1b51cx7fzyy4g7a0s7w-libpthread-stubs-0.4.drv
+   /gnu/store/8rigw1wzqpmhkxqj00svgaq78kg42x4z-pkg-config-0.29.2.drv
+[..]
+janneke@childhurd ~$ git config --global 
url."git+ssh://git.sv.gnu.org/srv/git/".insteadOf gnu:
+janneke@childhurd ~$ git clone gnu:guix
+Cloning into 'guix'...
+remote: Counting objects: 394436, done.
+remote: Compressing objects: 100% (85728/85728), done.
+remote: Total 394436 (delta 309572), reused 392294 (delta 307893)
+Receiving objects: 100% (394436/394436), 137.05 MiB | 1.18 MiB/s, done.
+Resolving deltas: 100% (309572/309572), done.
+Updating files: 100% (2199/2199), done.
+janneke@childhurd ~$ cd guix
+janneke@childhurd ~$ ./bootstrap
+[..]
+janneke@childhurd ~$ ./configure --with-courage
+janneke@childhurd ~$ make
+[..]
+janneke@childhurd ~$ ./pre-inst-env guix build hello
+[..]
+```
+
+just like we are used to.
+
+
+# What's next?
+
+In [an earlier post](https://guix.gnu.org/blog/2020/hello-hurd/) we
+tried to answer the question ``Why bother with the Hurd anyway?`` An
+obvious question because it is [all too easy to get
+discouraged](https://xkcd.com/1508), to downplay or underestimate the
+potential social impact of GNU and the Hurd.
+
+We tried to make Hurd development as easy and as pleasant as we
+could... but 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 discussend and is in progress right now is
+
+   * [user-space driver/modern hardware
+support](https://lists.gnu.org/archive/html/bug-hurd/2020-07/msg00042.html)
+   * Implementing [Hurd Audio
+support](https://nlnet.nl/project/Hurd-Audio/), sponsored by
+[NLnet](hthtps://nlnet.nl),
+   * [SMP
+support](https://lists.gnu.org/archive/html/bug-hurd/2020-07/msg00048.html),
+   * [64bit](https://github.com/etienne02/gnumach/tree/master/x86_64)/
+[x86_64](http://richtlijn.be/~larstiq/hurd/hurd-2020-03-28) support,
+non-Intel CPU support.
+
+Join `#guix` and `#hurd` on irc.freenode.net to get involved!
+
+#### About GNU Guix
+
+[GNU Guix](https://www.gnu.org/software/guix) is a transactional package
+manager and an advanced distribution of the GNU system that [respects
+user
+freedom](https://www.gnu.org/distros/free-system-distribution-guidelines.html).
+Guix can be used on top of any system running the Hurd or the Linux
+kernel, or it can be used as a standalone operating system distribution
+for i686, x86_64, ARMv7, and AArch64 machines.
+
+In addition to standard package management features, Guix supports
+transactional upgrades and roll-backs, unprivileged package management,
+per-user profiles, and garbage collection.  When used as a standalone
+GNU/Linux distribution, Guix offers a declarative, stateless approach to
+operating system configuration management.  Guix is highly customizable
+and hackable through [Guile](https://www.gnu.org/software/guile)
+programming interfaces and extensions to the
+[Scheme](http://schemers.org) language.
+
+#### About the GNU Hurd
+
+[The GNU Hurd](https://www.gnu.org/software/hurd) is the GNU project's
+replacement for the Unix kernel.  It is a collection of servers that
+run on the Mach microkernel to implement file systems, network
+protocols, file access control, and other features that are
+implemented by the Unix kernel or similar kernels (such as Linux).
+[More
+info](https://www.gnu.org/software/hurd/hurd/documentation.html).
+
+The [mission of the GNU
+Hurd](https://www.gnu.org/software/hurd/community/weblogs/antrik/hurd-mission-statement.html)
+project is to create a general-purpose kernel suitable for the GNU
+operating system, which is viable for everyday use, and gives users
+and programs as much control over their computing environment as
+possible.
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