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#!/usr/bin/python3
# Copyright 2024 Helmut Grohne <helmut@subdivi.de>
# SPDX-License-Identifier: GPL-3
"""Unshare a UTS (and user and mount) namespace and change the hostname."""
import os
import pathlib
import socket
import sys
import tempfile
if __file__.split("/")[-2:-1] == ["examples"]:
sys.path.insert(0, "/".join(__file__.split("/")[:-2]))
import linuxnamespaces
def change_file(location: pathlib.Path, content: bytes | str) -> None:
if isinstance(content, str):
content = content.encode("ascii")
try:
st = location.stat()
except FileNotFoundError as err:
raise ValueError(
f"cannot change non-existent file: {location!r}"
) from err
if st.st_size == len(content) and location.read_bytes() == content:
return
with tempfile.NamedTemporaryFile() as tfile:
tfile.write(content)
# In Python >= 3.12, we should set delete_on_close=False rather than
# closing the underlying file object behind tempfile's back.
tfile.file.close()
linuxnamespaces.bind_mount(tfile.name, location)
def main() -> None:
hostname = sys.argv[1]
linuxnamespaces.unshare_user_idmap(
[linuxnamespaces.IDMapping.identity(os.getuid())],
[linuxnamespaces.IDMapping.identity(os.getgid())],
linuxnamespaces.CloneFlags.NEWUSER
| linuxnamespaces.CloneFlags.NEWNS
| linuxnamespaces.CloneFlags.NEWUTS,
)
socket.sethostname(hostname)
etc = pathlib.Path("/etc")
change_file(etc / "hostname", f"{hostname}\n")
change_file(
etc / "hosts",
f"""127.0.0.1 {hostname} localhost
::1 {hostname} localhost
""",
)
os.execlp(os.environ["SHELL"], os.environ["SHELL"])
if __name__ == "__main__":
main()
|
