88 lines
5 KiB
Python
88 lines
5 KiB
Python
#!/usr/bin/python3
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import argparse
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import pathlib
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import subprocess
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import tempfile
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import pathlib
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__author__ = "Trent W. Buck"
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__copyright__ = "Copyright © 2020 Trent W. Buck"
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__license__ = "expat"
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__doc__ = """ build the simplest Debian Live image that can boot
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This uses mmdebstrap to do the heavy lifting;
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it can run entirely without root privileges.
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It emits a USB key disk image that contains a bootable EFI ESP,
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which in turn includes a bootloader (refind), kernel, ramdisk, and filesystem.squashfs.
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NOTE: this is the simplest config possible.
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It lacks CRITICAL SECURITY AND DATA LOSS packages, such as amd64-microcode and smartd.
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"""
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parser = argparse.ArgumentParser(description=__doc__)
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parser.add_argument('output_file', nargs='?', default=pathlib.Path('filesystem.img'), type=pathlib.Path)
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args = parser.parse_args()
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filesystem_img_size = '256M' # big enough to include filesystem.squashfs + about 64M of bootloader, kernel, and ramdisk.
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esp_offset = 1024 * 1024 # 1MiB
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esp_label = 'UEFI-ESP' # max 8 bytes for FAT32
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live_media_path = 'debian-live'
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with tempfile.TemporaryDirectory(prefix='debian-live-bullseye-amd64-minimal.') as td:
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td = pathlib.Path(td)
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subprocess.check_call(
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['mmdebstrap',
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'--mode=unshare',
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'--variant=apt',
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'--aptopt=Acquire::http::Proxy "http://apt-cacher-ng.cyber.com.au:3142"',
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'--aptopt=Acquire::https::Proxy "DIRECT"',
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'--dpkgopt=force-unsafe-io',
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'--include=linux-image-amd64 init initramfs-tools live-boot netbase',
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'--include=dbus', # https://bugs.debian.org/814758
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'--include=live-config iproute2 keyboard-configuration locales sudo user-setup',
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'--include=ifupdown isc-dhcp-client', # live-config doesn't support systemd-networkd yet.
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# Do the **BARE MINIMUM** to make a USB key that can boot on X86_64 UEFI.
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# We use mtools so we do not ever need root privileges.
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# We can't use mkfs.vfat, as that needs kpartx or losetup (i.e. root).
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# We can't use mkfs.udf, as that needs mount (i.e. root).
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# We can't use "refind-install --usedefault" as that runs mount(8) (i.e. root).
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# We don't use genisoimage because
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# 1) ISO9660 must die;
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# 2) incomplete UDF 1.5+ support;
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# 3) resulting filesystem can't be tweaked after flashing (e.g. debian-live/site.dir/etc/systemd/network/up.network).
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#
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# We use refind because 1) I hate grub; and 2) I like refind.
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# If you want aarch64 or ia32 you need to install their BOOTxxx.EFI files.
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# If you want kernel+initrd on something other than FAT, you need refind/drivers_xxx/xxx_xxx.EFI.
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#
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# FIXME: with qemu in UEFI mode (OVMF), I get dumped into startup.nsh (UEFI REPL).
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# From there, I can manually type in "FS0:\EFI\BOOT\BOOTX64.EFI" to start refind, tho.
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# So WTF is its problem? Does it not support fallback bootloader?
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'--include=refind parted mtools',
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'--essential-hook=echo refind refind/install_to_esp boolean false | chroot $1 debconf-set-selections',
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'--customize-hook=echo refind refind/install_to_esp boolean true | chroot $1 debconf-set-selections',
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'--customize-hook=chroot $1 mkdir -p /boot/USB /boot/EFI/BOOT',
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'--customize-hook=chroot $1 cp /usr/share/refind/refind/refind_x64.efi /boot/EFI/BOOT/BOOTX64.EFI',
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f'--customize-hook=chroot $1 truncate --size={filesystem_img_size} /boot/USB/filesystem.img',
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f'--customize-hook=chroot $1 parted --script --align=optimal /boot/USB/filesystem.img mklabel gpt mkpart {esp_label} {esp_offset}b 100% set 1 esp on',
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f'--customize-hook=chroot $1 mformat -i /boot/USB/filesystem.img@@{esp_offset} -F -v {esp_label}',
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f'--customize-hook=chroot $1 mmd -i /boot/USB/filesystem.img@@{esp_offset} ::{live_media_path}',
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f"""--customize-hook=echo '"Boot with default options" "boot=live live-media-path={live_media_path}"' >$1/boot/refind_linux.conf""",
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# NOTE: find sidesteps the "glob expands before chroot applies" problem.
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f"""--customize-hook=chroot $1 find -O3 /boot/ -xdev -mindepth 1 -maxdepth 1 -regextype posix-egrep -iregex '.*/(EFI|refind_linux.conf|vmlinuz.*|initrd.img.*)' -exec mcopy -vsbpm -i /boot/USB/filesystem.img@@{esp_offset} {{}} :: ';'""",
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# FIXME: copy-out doesn't handle sparseness, so is REALLY slow (about 50 seconds).
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# Therefore instead leave it in the squashfs, and extract it later.
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# f'--customize-hook=copy-out /boot/USB/filesystem.img /tmp/',
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# f'--customize-hook=chroot $1 rm /boot/USB/filesystem.img',
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'bullseye',
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td / 'filesystem.squashfs'
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])
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with args.output_file.open('wb') as f:
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subprocess.check_call(['rdsquashfs', '--cat=boot/USB/filesystem.img', td / 'filesystem.squashfs'], stdout=f)
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subprocess.check_call([
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'mcopy', '-i', f'{args.output_file}@@{esp_offset}', td / 'filesystem.squashfs', f'::{live_media_path}/filesystem.squashfs'])
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