7ea901928d
Create and instantiate the ext4 filesystem directly on the device, without ever mounting it. This means that only grub2 now requires loopback devices to function properly. Signed-off-by: Tom Gundersen <teg@jklm.no>
86 lines
3.4 KiB
Python
Executable file
86 lines
3.4 KiB
Python
Executable file
#!/usr/bin/python3
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import contextlib
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import json
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import math
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import os
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import shutil
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import subprocess
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import sys
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import tempfile
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def tree_size(tree):
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size = 0
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for root, dirs, files in os.walk(tree):
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for entry in files + dirs:
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path = os.path.join(root, entry)
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size += os.stat(path, follow_symlinks=False).st_size
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return size
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@contextlib.contextmanager
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def mount(source, dest, *options):
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os.makedirs(dest, 0o755, True)
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subprocess.run(["mount", *options, source, dest], check=True)
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try:
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yield
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finally:
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subprocess.run(["umount", "-R", dest], check=True)
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@contextlib.contextmanager
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def mount_api(dest):
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with mount("/dev", f"{dest}/dev", "-o", "rbind"), \
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mount("/proc", f"{dest}/proc", "-o", "rbind"), \
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mount("/sys", f"{dest}/sys", "-o", "rbind"), \
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mount("none", f"{dest}/run", "-t", "tmpfs"):
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yield
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@contextlib.contextmanager
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def loop_device(image, size, offset=0):
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r = subprocess.run(["losetup", "--partscan", "--show", "--find", "--sizelimit", str(size), "--offset", str(offset), image], stdout=subprocess.PIPE, encoding="utf-8", check=True)
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loop = r.stdout.strip()
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try:
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yield loop
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finally:
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subprocess.run(["losetup", "-d", loop], check=True)
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def main(tree, output_dir, options):
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filename = options["filename"]
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partition_table_id = options["partition_table_id"]
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root_fs_uuid = options["root_fs_uuid"]
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# Create a working directory on a tmpfs, maybe we should implicitly
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# always do this.
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with tempfile.TemporaryDirectory() as workdir:
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image = f"{workdir}/image.raw"
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mountpoint = f"{workdir}/mnt"
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# Create an empty image file of the right size
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size = int(math.ceil(tree_size(tree) * 1.2 / 512) * 512)
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subprocess.run(["truncate", "--size", str(size), image], check=True)
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# Set up the partition table of the image
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partition_table = "label: mbr\nlabel-id: {partition_table_id}\nbootable, type=83"
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subprocess.run(["sfdisk", "-q", image], input=partition_table, encoding='utf-8', check=True)
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r = subprocess.run(["sfdisk", "--json", image], stdout=subprocess.PIPE, encoding='utf-8', check=True)
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partition_table = json.loads(r.stdout)
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partition = partition_table["partitiontable"]["partitions"][0]
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partition_offset = partition["start"] * 512
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partition_size = partition["size"] * 512
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# Populate the first partition of the image with an ext4 fs and fill it with the contents of the
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# tree we are operating on.
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subprocess.run(["mkfs.ext4", "-d", tree, "-U", root_fs_uuid, "-E", f"offset={partition_offset}", image, f"{int(partition_size / 1024)}k"], input="y", encoding='utf-8', check=True)
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# Mount the created image as a loopback device
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with loop_device(image, size) as loop, \
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mount(f"{loop}p1", mountpoint):
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# Install grub2 into the boot sector of the image, and copy the grub2 imagise into /boot/grub2
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with mount_api(mountpoint):
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subprocess.run(["chroot", mountpoint, "grub2-install", "--no-floppy", "--target", "i386-pc", loop], check=True)
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subprocess.run(["qemu-img", "convert", "-O" "qcow2", "-c", image, f"{output_dir}/{filename}"], check=True)
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if __name__ == '__main__':
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args = json.load(sys.stdin)
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r = main(args["tree"], args["output_dir"], args["options"])
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sys.exit(r)
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