nixos: Add derivations for SD card installation images on ARM

The resulting image can be copied to a SD card with `dd` and is directly
bootable by a suitably configured U-Boot. Though depending on the board, some
extra steps are required for copying U-Boot itself to the SD card.

Inside the image is a partition table, with a FAT32 /boot and a normal
writable EXT4 rootfs. It's possible to directly reuse the SD image's
partition layout and "install" NixOS on the same SD card by replacing
the default configuration.nix and nixos-rebuild, and actually is the
preferred way to use these images. To assist in this installation
method, the boot scripts on the image automatically resize the rootfs
partition to fit the SD card on the first boot.

The SD images come in two flavors; one for the ARMv6 Raspberry Pi,
and one multiplatform image for all the boards supported by the
mainline kernel's multi_v7_defconfig config target. At the moment, these
have been tested on:
    - Raspberry Pi Model B (512MB model)
    - NVIDIA Jetson TK1
    - Linksprite pcDuino3 Nano

To build, run:

nix-build '<nixpkgs/nixos>' -A config.system.build.sdImage \
    -I nixos-config='<nixpkgs/nixos/modules/installer/cd-dvd/sd-image-armv7l-multiplatform.nix>'
This commit is contained in:
Tuomas Tynkkynen 2015-05-05 06:23:28 +03:00
parent 8665b0d8b1
commit df86813d97
4 changed files with 301 additions and 0 deletions

View File

@ -0,0 +1,88 @@
# Builds an ext4 image containing a populated /nix/store with the closure
# of store paths passed in the storePaths parameter. The generated image
# is sized to only fit its contents, with the expectation that a script
# resizes the filesystem at boot time.
{ pkgs
, storePaths
, volumeLabel
}:
pkgs.stdenv.mkDerivation {
name = "ext4-fs.img";
buildInputs = with pkgs; [e2fsprogs libfaketime perl];
# For obtaining the closure of `storePaths'.
exportReferencesGraph =
map (x: [("closure-" + baseNameOf x) x]) storePaths;
buildCommand =
''
# Add the closures of the top-level store objects.
storePaths=$(perl ${pkgs.pathsFromGraph} closure-*)
# Also include a manifest of the closures in a format suitable
# for nix-store --load-db.
printRegistration=1 perl ${pkgs.pathsFromGraph} closure-* > nix-path-registration
# Make a crude approximation of the size of the target image.
# If the script starts failing, increase the fudge factors here.
numInodes=$(find $storePaths | wc -l)
numDataBlocks=$(du -c -B 4096 --apparent-size $storePaths | awk '$2 == "total" { print int($1 * 1.03) }')
bytes=$((2 * 4096 * $numInodes + 4096 * $numDataBlocks))
echo "Creating an EXT4 image of $bytes bytes (numInodes=$numInodes, numDataBlocks=$numDataBlocks)"
truncate -s $bytes $out
faketime "1970-01-01 00:00:00" mkfs.ext4 -L ${volumeLabel} -U 44444444-4444-4444-8888-888888888888 $out
# Populate the image contents by piping a bunch of commands to the `debugfs` tool from e2fsprogs.
# For example, to copy /nix/store/abcd...efg-coreutils-8.23/bin/sleep:
# cd /nix/store/abcd...efg-coreutils-8.23/bin
# write /nix/store/abcd...efg-coreutils-8.23/bin/sleep sleep
# sif sleep mode 040555
# sif sleep gid 30000
# In particular, debugfs doesn't handle absolute target paths; you have to 'cd' in the virtual
# filesystem first. Likewise the intermediate directories must already exist (using `find`
# handles that for us). And when setting the file's permissions, the inode type flags (__S_IFDIR,
# __S_IFREG) need to be set as well.
(
echo write nix-path-registration nix-path-registration
echo mkdir nix
echo cd /nix
echo mkdir store
# XXX: This explodes in exciting ways if anything in /nix/store has a space in it.
find $storePaths -printf '%y %f %h %m\n'| while read -r type file dir perms; do
# echo "TYPE=$type DIR=$dir FILE=$file PERMS=$perms" >&2
echo "cd $dir"
case $type in
d)
echo "mkdir $file"
echo sif $file mode $((040000 | 0$perms)) # magic constant is __S_IFDIR
;;
f)
echo "write $dir/$file $file"
echo sif $file mode $((0100000 | 0$perms)) # magic constant is __S_IFREG
;;
l)
echo "symlink $file $(readlink "$dir/$file")"
;;
*)
echo "Unknown entry: $type $dir $file $perms" >&2
exit 1
;;
esac
echo sif $file gid 30000 # chgrp to nixbld
done
) | faketime "1970-01-01 00:00:00" debugfs -w $out -f /dev/stdin > errorlog 2>&1
# The debugfs tool doesn't terminate on error nor exit with a non-zero status. Check manually.
if egrep -q 'Could not allocate|File not found' errorlog; then
cat errorlog
echo "--- Failed to create EXT4 image of $bytes bytes (numInodes=$numInodes, numDataBlocks=$numDataBlocks) ---"
return 1
fi
'';
}

View File

@ -0,0 +1,40 @@
{ config, lib, pkgs, ... }:
let
extlinux-conf-builder =
import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
inherit pkgs;
};
in
{
imports = [
../../profiles/minimal.nix
../../profiles/installation-device.nix
./sd-image.nix
];
assertions = lib.singleton {
assertion = pkgs.stdenv.system == "armv7l-linux";
message = "sd-image-armv7l-multiplatform.nix can be only built natively on ARMv7; " +
"it cannot be cross compiled";
};
boot.loader.grub.enable = false;
boot.loader.generic-extlinux-compatible.enable = true;
# FIXME: change this to linuxPackages_latest once v4.2 is out
boot.kernelPackages = pkgs.linuxPackages_testing;
boot.kernelParams = ["console=ttyS0,115200n8" "console=ttyAMA0,115200n8" "console=tty0"];
# FIXME: fix manual evaluation on ARM
services.nixosManual.enable = lib.mkOverride 0 false;
# FIXME: this probably should be in installation-device.nix
users.extraUsers.root.initialHashedPassword = "";
sdImage = {
populateBootCommands = ''
${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./boot
'';
};
}

View File

@ -0,0 +1,46 @@
{ config, lib, pkgs, ... }:
let
extlinux-conf-builder =
import ../../system/boot/loader/generic-extlinux-compatible/extlinux-conf-builder.nix {
inherit pkgs;
};
in
{
imports = [
../../profiles/minimal.nix
../../profiles/installation-device.nix
./sd-image.nix
];
assertions = lib.singleton {
assertion = pkgs.stdenv.system == "armv6l-linux";
message = "sd-image-raspberrypi.nix can be only built natively on ARMv6; " +
"it cannot be cross compiled";
};
# Needed by RPi firmware
nixpkgs.config.allowUnfree = true;
boot.loader.grub.enable = false;
boot.loader.generic-extlinux-compatible.enable = true;
boot.kernelPackages = pkgs.linuxPackages_rpi;
# FIXME: fix manual evaluation on ARM
services.nixosManual.enable = lib.mkOverride 0 false;
# FIXME: this probably should be in installation-device.nix
users.extraUsers.root.initialHashedPassword = "";
sdImage = {
populateBootCommands = ''
for f in bootcode.bin fixup.dat start.elf; do
cp ${pkgs.raspberrypifw}/share/raspberrypi/boot/$f boot/
done
cp ${pkgs.ubootRaspberryPi}/u-boot.bin boot/u-boot-rpi.bin
echo 'kernel u-boot-rpi.bin' > boot/config.txt
${extlinux-conf-builder} -t 3 -c ${config.system.build.toplevel} -d ./boot
'';
};
}

View File

@ -0,0 +1,127 @@
# This module creates a bootable SD card image containing the given NixOS
# configuration. The generated image is MBR partitioned, with a FAT /boot
# partition, and ext4 root partition. The generated image is sized to fit
# its contents, and a boot script automatically resizes the root partition
# to fit the device on the first boot.
#
# The derivation for the SD image will be placed in
# config.system.build.sdImage
{ config, lib, pkgs, ... }:
with lib;
let
rootfsImage = import ../../../lib/make-ext4-fs.nix {
inherit pkgs;
inherit (config.sdImage) storePaths;
volumeLabel = "NIXOS_SD";
};
in
{
options.sdImage = {
storePaths = mkOption {
type = with types; listOf package;
example = literalExample "[ pkgs.stdenv ]";
description = ''
Derivations to be included in the Nix store in the generated SD image.
'';
};
bootSize = mkOption {
type = types.int;
default = 128;
description = ''
Size of the /boot partition, in megabytes.
'';
};
populateBootCommands = mkOption {
example = literalExample "'' cp \${pkgs.myBootLoader}/u-boot.bin boot/ ''";
description = ''
Shell commands to populate the ./boot directory.
All files in that directory are copied to the
/boot partition on the SD image.
'';
};
};
config = {
fileSystems = {
"/boot" = {
device = "/dev/disk/by-label/NIXOS_BOOT";
fsType = "vfat";
};
"/" = {
device = "/dev/disk/by-label/NIXOS_SD";
fsType = "ext4";
};
};
sdImage.storePaths = [ config.system.build.toplevel ];
system.build.sdImage = pkgs.stdenv.mkDerivation {
name = "sd-image-${pkgs.stdenv.system}.img";
buildInputs = with pkgs; [ dosfstools e2fsprogs mtools libfaketime utillinux ];
buildCommand = ''
# Create the image file sized to fit /boot and /, plus 4M of slack
rootSizeBlocks=$(du -B 512 --apparent-size ${rootfsImage} | awk '{ print $1 }')
bootSizeBlocks=$((${toString config.sdImage.bootSize} * 1024 * 1024 / 512))
imageSize=$((rootSizeBlocks * 512 + bootSizeBlocks * 512 + 4096 * 1024))
truncate -s $imageSize $out
# type=b is 'W95 FAT32', type=83 is 'Linux'.
sfdisk $out <<EOF
label: dos
label-id: 0x2178694e
start=1M, size=$bootSizeBlocks, type=b, bootable
type=83
EOF
# Copy the rootfs into the SD image
eval $(partx $out -o START,SECTORS --nr 2 --pairs)
dd conv=notrunc if=${rootfsImage} of=$out seek=$START count=$SECTORS
# Create a FAT32 /boot partition of suitable size into bootpart.img
eval $(partx $out -o START,SECTORS --nr 1 --pairs)
truncate -s $((SECTORS * 512)) bootpart.img
faketime "1970-01-01 00:00:00" mkfs.vfat -i 0x2178694e -n NIXOS_BOOT bootpart.img
# Populate the files intended for /boot
mkdir boot
${config.sdImage.populateBootCommands}
# Copy the populated /boot into the SD image
(cd boot; mcopy -bpsvm -i ../bootpart.img ./* ::)
dd conv=notrunc if=bootpart.img of=$out seek=$START count=$SECTORS
'';
};
boot.postBootCommands = ''
# On the first boot do some maintenance tasks
if [ -f /nix-path-registration ]; then
# Figure out device names for the boot device and root filesystem.
rootPart=$(readlink -f /dev/disk/by-label/NIXOS_SD)
bootDevice=$(lsblk -npo PKNAME $rootPart)
# Resize the root partition and the filesystem to fit the disk
echo ",+," | sfdisk -N2 --no-reread $bootDevice
${pkgs.parted}/bin/partprobe
${pkgs.e2fsprogs}/bin/resize2fs $rootPart
# Register the contents of the initial Nix store
${config.nix.package}/bin/nix-store --load-db < /nix-path-registration
# nixos-rebuild also requires a "system" profile and an /etc/NIXOS tag.
touch /etc/NIXOS
${config.nix.package}/bin/nix-env -p /nix/var/nix/profiles/system --set /run/current-system
# Prevents this from running on later boots.
rm -f /nix-path-registration
fi
'';
};
}