431 lines
15 KiB
Scheme
431 lines
15 KiB
Scheme
;;; GNU Guix --- Functional package management for GNU
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;;; Copyright © 2013, 2014, 2015, 2016 Ludovic Courtès <ludo@gnu.org>
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;;;
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;;; This file is part of GNU Guix.
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;;;
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;;; GNU Guix is free software; you can redistribute it and/or modify it
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;;; under the terms of the GNU General Public License as published by
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;;; the Free Software Foundation; either version 3 of the License, or (at
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;;; your option) any later version.
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;;;
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;;; GNU Guix is distributed in the hope that it will be useful, but
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;;; WITHOUT ANY WARRANTY; without even the implied warranty of
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;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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;;; GNU General Public License for more details.
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;;;
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;;; You should have received a copy of the GNU General Public License
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;;; along with GNU Guix. If not, see <http://www.gnu.org/licenses/>.
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(define-module (gnu build linux-boot)
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#:use-module (rnrs io ports)
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#:use-module (system repl error-handling)
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#:autoload (system repl repl) (start-repl)
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#:autoload (system base compile) (compile-file)
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-26)
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#:use-module (ice-9 match)
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#:use-module (ice-9 ftw)
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#:use-module (guix build utils)
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#:use-module (gnu build linux-modules)
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#:use-module (gnu build file-systems)
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#:export (mount-essential-file-systems
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linux-command-line
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find-long-option
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make-essential-device-nodes
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configure-qemu-networking
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bind-mount
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device-number
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boot-system))
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;;; Commentary:
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;;;
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;;; Utility procedures useful in a Linux initial RAM disk (initrd). Note that
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;;; many of these use procedures not yet available in vanilla Guile (`mount',
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;;; `load-linux-module', etc.); these are provided by a Guile patch used in
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;;; the GNU distribution.
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;;;
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;;; Code:
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(define* (mount-essential-file-systems #:key (root "/"))
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"Mount /dev, /proc, and /sys under ROOT."
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(define (scope dir)
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(string-append root
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(if (string-suffix? "/" root)
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""
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"/")
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dir))
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(unless (file-exists? (scope "proc"))
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(mkdir (scope "proc")))
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(mount "none" (scope "proc") "proc")
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(unless (file-exists? (scope "dev"))
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(mkdir (scope "dev")))
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(mount "none" (scope "dev") "devtmpfs")
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(unless (file-exists? (scope "sys"))
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(mkdir (scope "sys")))
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(mount "none" (scope "sys") "sysfs"))
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(define (move-essential-file-systems root)
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"Move currently mounted essential file systems to ROOT."
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(for-each (lambda (dir)
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(let ((target (string-append root dir)))
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(unless (file-exists? target)
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(mkdir target))
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(mount dir target "" MS_MOVE)))
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'("/dev" "/proc" "/sys")))
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(define (linux-command-line)
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"Return the Linux kernel command line as a list of strings."
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(string-tokenize
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(call-with-input-file "/proc/cmdline"
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get-string-all)))
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(define (find-long-option option arguments)
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"Find OPTION among ARGUMENTS, where OPTION is something like \"--load\".
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Return the value associated with OPTION, or #f on failure."
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(let ((opt (string-append option "=")))
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(and=> (find (cut string-prefix? opt <>)
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arguments)
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(lambda (arg)
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(substring arg (+ 1 (string-index arg #\=)))))))
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(define* (make-disk-device-nodes base major #:optional (minor 0))
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"Make the block device nodes around BASE (something like \"/root/dev/sda\")
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with the given MAJOR number, starting with MINOR."
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(mknod base 'block-special #o644 (device-number major minor))
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(let loop ((i 1))
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(when (< i 16)
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(mknod (string-append base (number->string i))
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'block-special #o644 (device-number major (+ minor i)))
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(loop (+ i 1)))))
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(define* (make-essential-device-nodes #:key (root "/"))
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"Make essential device nodes under ROOT/dev."
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;; The hand-made devtmpfs/udev!
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(define (scope dir)
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(string-append root
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(if (string-suffix? "/" root)
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""
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"/")
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dir))
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(unless (file-exists? (scope "dev"))
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(mkdir (scope "dev")))
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;; Make the device nodes for SCSI disks.
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(make-disk-device-nodes (scope "dev/sda") 8)
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(make-disk-device-nodes (scope "dev/sdb") 8 16)
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(make-disk-device-nodes (scope "dev/sdc") 8 32)
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(make-disk-device-nodes (scope "dev/sdd") 8 48)
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;; SCSI CD-ROM devices (aka. "/dev/sr0" etc.).
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(mknod (scope "dev/scd0") 'block-special #o644 (device-number 11 0))
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(mknod (scope "dev/scd1") 'block-special #o644 (device-number 11 1))
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;; The virtio (para-virtualized) block devices, as supported by QEMU/KVM.
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(make-disk-device-nodes (scope "dev/vda") 252)
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;; Memory (used by Xorg's VESA driver.)
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(mknod (scope "dev/mem") 'char-special #o640 (device-number 1 1))
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(mknod (scope "dev/kmem") 'char-special #o640 (device-number 1 2))
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;; Inputs (used by Xorg.)
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(unless (file-exists? (scope "dev/input"))
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(mkdir (scope "dev/input")))
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(mknod (scope "dev/input/mice") 'char-special #o640 (device-number 13 63))
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(mknod (scope "dev/input/mouse0") 'char-special #o640 (device-number 13 32))
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(mknod (scope "dev/input/event0") 'char-special #o640 (device-number 13 64))
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;; System console. This node is magically created by the kernel on the
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;; initrd's root, so don't try to create it in that case.
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(unless (string=? root "/")
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(mknod (scope "dev/console") 'char-special #o600
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(device-number 5 1)))
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;; TTYs.
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(mknod (scope "dev/tty") 'char-special #o600
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(device-number 5 0))
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(chmod (scope "dev/tty") #o666)
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(let loop ((n 0))
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(and (< n 50)
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(let ((name (format #f "dev/tty~a" n)))
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(mknod (scope name) 'char-special #o600
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(device-number 4 n))
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(loop (+ 1 n)))))
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;; Serial line.
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(mknod (scope "dev/ttyS0") 'char-special #o660
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(device-number 4 64))
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;; Pseudo ttys.
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(mknod (scope "dev/ptmx") 'char-special #o666
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(device-number 5 2))
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(chmod (scope "dev/ptmx") #o666)
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;; Create /dev/pts; it will be mounted later, at boot time.
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(unless (file-exists? (scope "dev/pts"))
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(mkdir (scope "dev/pts")))
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;; Rendez-vous point for syslogd.
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(mknod (scope "dev/log") 'socket #o666 0)
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(mknod (scope "dev/kmsg") 'char-special #o600 (device-number 1 11))
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;; Other useful nodes, notably relied on by guix-daemon.
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(for-each (match-lambda
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((file major minor)
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(mknod (scope file) 'char-special #o666
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(device-number major minor))
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(chmod (scope file) #o666)))
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'(("dev/null" 1 3)
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("dev/zero" 1 5)
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("dev/full" 1 7)
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("dev/random" 1 8)
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("dev/urandom" 1 9)))
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(symlink "/proc/self/fd" (scope "dev/fd"))
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(symlink "/proc/self/fd/0" (scope "dev/stdin"))
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(symlink "/proc/self/fd/1" (scope "dev/stdout"))
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(symlink "/proc/self/fd/2" (scope "dev/stderr"))
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;; Loopback devices.
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(let loop ((i 0))
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(when (< i 8)
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(mknod (scope (string-append "dev/loop" (number->string i)))
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'block-special #o660
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(device-number 7 i))
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(loop (+ 1 i))))
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;; File systems in user space (FUSE).
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(mknod (scope "dev/fuse") 'char-special #o666 (device-number 10 229)))
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(define %host-qemu-ipv4-address
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(inet-pton AF_INET "10.0.2.10"))
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(define* (configure-qemu-networking #:optional (interface "eth0"))
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"Setup the INTERFACE network interface and /etc/resolv.conf according to
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QEMU's default networking settings (see net/slirp.c in QEMU for default
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networking values.) Return #t if INTERFACE is up, #f otherwise."
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(display "configuring QEMU networking...\n")
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(let* ((sock (socket AF_INET SOCK_STREAM 0))
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(address (make-socket-address AF_INET %host-qemu-ipv4-address 0))
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(flags (network-interface-flags sock interface)))
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(set-network-interface-address sock interface address)
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(set-network-interface-flags sock interface (logior flags IFF_UP))
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;; Hello! We used to create /etc/resolv.conf here, with "nameserver
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;; 10.0.2.3\n". However, with Linux-libre 3.16, we're getting ENOSPC.
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;; And since it's actually unnecessary, it's gone.
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(logand (network-interface-flags sock interface) IFF_UP)))
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(define (device-number major minor)
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"Return the device number for the device with MAJOR and MINOR, for use as
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the last argument of `mknod'."
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(+ (* major 256) minor))
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(define (pidof program)
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"Return the PID of the first presumed instance of PROGRAM."
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(let ((program (basename program)))
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(find (lambda (pid)
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(let ((exe (format #f "/proc/~a/exe" pid)))
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(and=> (false-if-exception (readlink exe))
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(compose (cut string=? program <>) basename))))
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(filter-map string->number (scandir "/proc")))))
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(define* (mount-root-file-system root type
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#:key volatile-root? (unionfs "unionfs"))
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"Mount the root file system of type TYPE at device ROOT. If VOLATILE-ROOT?
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is true, mount ROOT read-only and make it a union with a writable tmpfs using
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UNIONFS."
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(define (mark-as-not-killable pid)
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;; Tell the 'user-processes' shepherd service that PID must be kept alive
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;; when shutting down.
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(mkdir-p "/root/etc/shepherd")
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(let ((port (open-file "/root/etc/shepherd/do-not-kill" "a")))
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(chmod port #o600)
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(write pid port)
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(newline port)
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(close-port port)))
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(if volatile-root?
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(begin
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(mkdir-p "/real-root")
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(mount root "/real-root" type MS_RDONLY)
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(mkdir-p "/rw-root")
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(mount "none" "/rw-root" "tmpfs")
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;; We want read-write /dev nodes.
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(mkdir-p "/rw-root/dev")
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(mount "none" "/rw-root/dev" "devtmpfs")
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;; Make /root a union of the tmpfs and the actual root. Use
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;; 'max_files' to set a high RLIMIT_NOFILE for the unionfs process
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;; itself. Failing to do that, we quickly run out of file
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;; descriptors; see <http://bugs.gnu.org/17827>.
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(unless (zero? (system* unionfs "-o"
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"cow,allow_other,use_ino,suid,dev,max_files=65536"
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"/rw-root=RW:/real-root=RO"
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"/root"))
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(error "unionfs failed"))
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;; Make sure unionfs remains alive till the end. Because
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;; 'fuse_daemonize' doesn't tell the PID of the forked daemon, we
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;; have to resort to 'pidof' here.
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(mark-as-not-killable (pidof unionfs)))
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(begin
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(check-file-system root type)
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(mount root "/root" type)))
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;; Make sure /root/etc/mtab is a symlink to /proc/self/mounts.
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(false-if-exception
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(delete-file "/root/etc/mtab"))
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(symlink "/proc/self/mounts" "/root/etc/mtab"))
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(define (switch-root root)
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"Switch to ROOT as the root file system, in a way similar to what
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util-linux' switch_root(8) does."
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(move-essential-file-systems root)
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(chdir root)
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;; Since we're about to 'rm -rf /', try to make sure we're on an initrd.
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;; TODO: Use 'statfs' to check the fs type, like klibc does.
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(when (or (not (file-exists? "/init")) (directory-exists? "/home"))
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(format (current-error-port)
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"The root file system is probably not an initrd; \
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bailing out.~%root contents: ~s~%" (scandir "/"))
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(force-output (current-error-port))
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(exit 1))
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;; Delete files from the old root, without crossing mount points (assuming
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;; there are no mount points in sub-directories.) That means we're leaving
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;; the empty ROOT directory behind us, but that's OK.
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(let ((root-device (stat:dev (stat "/"))))
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(for-each (lambda (file)
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(unless (member file '("." ".."))
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(let* ((file (string-append "/" file))
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(device (stat:dev (lstat file))))
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(when (= device root-device)
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(delete-file-recursively file)))))
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(scandir "/")))
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;; Make ROOT the new root.
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(mount root "/" "" MS_MOVE)
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(chroot ".")
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(chdir "/")
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(when (file-exists? "/dev/console")
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;; Close the standard file descriptors since they refer to the old
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;; /dev/console, and reopen them.
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(let ((console (open-file "/dev/console" "r+b0")))
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(for-each close-fdes '(0 1 2))
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(dup2 (fileno console) 0)
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(dup2 (fileno console) 1)
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(dup2 (fileno console) 2)
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(close-port console))))
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(define* (boot-system #:key
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(linux-modules '())
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linux-module-directory
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qemu-guest-networking?
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volatile-root?
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pre-mount
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(mounts '()))
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"This procedure is meant to be called from an initrd. Boot a system by
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first loading LINUX-MODULES (a list of module names) from
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LINUX-MODULE-DIRECTORY, then setting up QEMU guest networking if
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QEMU-GUEST-NETWORKING? is true, calling PRE-MOUNT, mounting the file systems
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specified in MOUNTS, and finally booting into the new root if any. The initrd
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supports kernel command-line options '--load', '--root', and '--repl'.
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Mount the root file system, specified by the '--root' command-line argument,
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if any.
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MOUNTS must be a list suitable for 'mount-file-system'.
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When VOLATILE-ROOT? is true, the root file system is writable but any changes
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to it are lost."
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(define root-mount-point?
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(match-lambda
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((device _ "/" _ ...) #t)
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(_ #f)))
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(define root-fs-type
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(or (any (match-lambda
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((device _ "/" type _ ...) type)
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(_ #f))
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mounts)
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"ext4"))
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(define (lookup-module name)
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(string-append linux-module-directory "/"
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(ensure-dot-ko name)))
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(display "Welcome, this is GNU's early boot Guile.\n")
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(display "Use '--repl' for an initrd REPL.\n\n")
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(call-with-error-handling
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(lambda ()
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(mount-essential-file-systems)
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(let* ((args (linux-command-line))
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(to-load (find-long-option "--load" args))
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(root (find-long-option "--root" args)))
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(when (member "--repl" args)
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(start-repl))
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(display "loading kernel modules...\n")
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(for-each (cut load-linux-module* <>
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#:lookup-module lookup-module)
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(map lookup-module linux-modules))
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(when qemu-guest-networking?
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(unless (configure-qemu-networking)
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(display "network interface is DOWN\n")))
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;; Prepare the real root file system under /root.
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(unless (file-exists? "/root")
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(mkdir "/root"))
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(when (procedure? pre-mount)
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;; Do whatever actions are needed before mounting the root file
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;; system--e.g., installing device mappings. Error out when the
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;; return value is false.
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(unless (pre-mount)
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(error "pre-mount actions failed")))
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(if root
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(mount-root-file-system (canonicalize-device-spec root)
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root-fs-type
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#:volatile-root? volatile-root?)
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(mount "none" "/root" "tmpfs"))
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;; Mount the specified file systems.
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(for-each mount-file-system
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(remove root-mount-point? mounts))
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(if to-load
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(begin
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(switch-root "/root")
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(format #t "loading '~a'...\n" to-load)
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(primitive-load to-load)
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(format (current-error-port)
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"boot program '~a' terminated, rebooting~%"
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to-load)
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(sleep 2)
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(reboot))
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(begin
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(display "no boot file passed via '--load'\n")
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(display "entering a warm and cozy REPL\n")
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(start-repl)))))))
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;;; linux-initrd.scm ends here
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