Boot-to-Guile!

Boot-to-Guile!

[Ludovic Courtès]

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Hello!

To celebrate Guile 2.0’s second anniversary [0], I’m happy to announce
this Boot-to-Guile QEMU image!

  http://www.fdn.fr/~lcourtes/software/guix/boot-to-guile.qcow2

  sha1: c796a91be2efcae192a4032c13821c52ea9db07f
  sig:  http://www.fdn.fr/~lcourtes/software/guix/boot-to-guile.qcow2.asc

You can run it with:

  qemu-system-x86_64 qemu-image.qcow2

Or, even better, with networking and an SMB share with the host:

  qemu-system-x86_64 -net nic,model=e1000 -net user,smb=$PWD \
                     -hda qemu-image.qcow2

You will be dropped into a familiar & friendly REPL, run straight from
the initrd!  Neat, no?  :-)


The build process for this image is automated with GNU Guix (it can be
built by calling ‘example2’ in the (gnu system vm) module.)

The initrd in the image contains just a statically-linked Guile and a
few Linux modules.  So first, to do things one normally do in an initrd,
Guile needed to be extended with new procedures: ‘mount’, ‘reboot’,
‘set-network-interface-address’, etc. [1]

Second, the build process of initrd images needed to be automated.  So
the ‘expression->initrd’ procedure takes an expression, a list of Linux
modules to add to the initrd, and returns an initrd that runs Guile to
evaluate the given expression [2].

Third, we need an actual initrd that does useful things at boot time,
such as mounting /proc and the host SMB/CIFS share setup by QEMU.  The
actual code that runs is at [3].  Notice the lovely uses of
‘load-linux-module’, networking primitives, along with ‘start-repl’.  :-)

Fourth, we need a way to create a disk image, partition it, and install
GRUB on it.  This requires root privileges on GNU/Linux, so we do it in
a VM.  The ‘expression->derivation-in-linux-vm’ runs an expression in a
VM running the Linux-Libre kernel, using QEMU’s ability to directly boot
a Linux kernel for that [4].

Finally, the ‘qemu-image’ procedure builds the final, stand-alone disk
image, with its partition table, GRUB, etc. [5].


A long way!  My initial intent for the potluck was actually quite
different: I wanted to push Guile in the init process, via the nice dmd
released some time ago [6,7].  Something for the next few weeks/months.
Guile everywhere!

Happy birthday, Guile 2.0!

Ludo’.

[0] http://lists.gnu.org/archive/html/guile-user/2013-01/msg00007.html
[1] http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/patches/guile-linux-syscalls.patch
[2] http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/linux-initrd.scm#n41
[3] http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/packages/linux-initrd.scm#n174
[4] http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/vm.scm#n43
[5] http://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/vm.scm#n144
[6] http://lists.gnu.org/archive/html/guile-user/2003-04/msg00007.html
[7] https://gitorious.org/guix/dmd

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Re: Boot-to-Guile!

[Mike Gran]

> From: Ludovic Courtès <ludo@gnu.org>

> Hello!
> 
> To celebrate Guile 2.0’s second anniversary [0], I’m happy to announce
> this Boot-to-Guile QEMU image!

Amazing.

...

> Third, we need an actual initrd that does useful things at boot time,
> such as mounting /proc and the host SMB/CIFS share setup by QEMU.  The
> actual code that runs is at [3].  Notice the lovely uses of
> ‘load-linux-module’, networking primitives, along with ‘start-repl’.  :-)

  scheme@(guile-user)> (scandir "bin")
  $12 = ("." ".." "guile")

Cool.

Here's a fun message specific to your hack.

  scheme@(guile-user)> (getgroups)
  ERROR: In procedure getgroups:
  ERROR: In procedure getgroups: Success

-Mike Gran

Re: Boot-to-Guile!

[Ludovic Courtès]

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Mike Gran <spk121@yahoo.com> skribis:

> Here's a fun message specific to your hack.
>
>   scheme@(guile-user)> (getgroups)
>   ERROR: In procedure getgroups:
>   ERROR: In procedure getgroups: Success

Heh, funny.  :-)

Actually you found a bug, fixed like this:


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diff --git a/libguile/posix.c b/libguile/posix.c
index 324f21b..52ade13 100644
--- a/libguile/posix.c
+++ b/libguile/posix.c
@@ -265,8 +265,10 @@ SCM_DEFINE (scm_getgroups, "getgroups", 0, 0, 0,
   GETGROUPS_T *groups;
 
   ngroups = getgroups (0, NULL);
-  if (ngroups <= 0)
+  if (ngroups < 0)
     SCM_SYSERROR;
+  else if (ngroups == 0)
+    return scm_c_make_vector (0, SCM_BOOL_F);
 
   size = ngroups * sizeof (GETGROUPS_T);
   groups = scm_malloc (size);

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Thanks!

Ludo’.

Re: Boot-to-Guile!

[Aleix Conchillo Flaqué]

On Sat, Feb 16, 2013 at 3:59 AM, Ludovic Courtès <ludo@gnu.org> wrote:
> Hello!
>
> To celebrate Guile 2.0’s second anniversary [0], I’m happy to announce
> this Boot-to-Guile QEMU image!
>
>   http://www.fdn.fr/~lcourtes/software/guix/boot-to-guile.qcow2
>

Just tried it. Three words: this is fantastic!

Aleix

Re: Boot-to-Guile!

[Mark H Weaver]

Wow.  This is very exciting work, Ludovic.
You make our lives brighter :)

      Mark