Boot-to-Guile!

From: Ludovic Courtès Subject: Boot-to-Guile! Date: Sat, 16 Feb 2013 12:59:13 +0100 User-agent: Gnus/5.130005 (Ma Gnus v0.5) Emacs/24.2 (gnu/linux)

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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