flash: Fix gnome automounting bug

pkgs/clan-cli/clan_cli/flash.py

@@ -5,7 +5,8 @@ import logging
 import os
 import shutil
 import textwrap
-from collections.abc import Sequence
+from collections.abc import Generator, Sequence
+from contextlib import contextmanager
 from dataclasses import dataclass, field
 from pathlib import Path
 from tempfile import TemporaryDirectory
@@ -37,6 +38,60 @@ class SystemConfig:
     wifi_settings: list[WifiConfig] | None = field(default=None)
 
 
+@contextmanager
+def pause_automounting(
+    devices: list[Path], no_udev: bool
+) -> Generator[None, None, None]:
+    """
+    Pause automounting on the device for the duration of this context
+    manager
+    """
+    if no_udev:
+        yield None
+        return
+
+    if shutil.which("udevadm") is None:
+        msg = "udev is required to disable automounting"
+        log.warning(msg)
+        yield None
+        return
+
+    if os.geteuid() != 0:
+        msg = "root privileges are required to disable automounting"
+        raise ClanError(msg)
+    try:
+        # See /usr/lib/udisks2/udisks2-inhibit
+        rules_dir = Path("/run/udev/rules.d")
+        rules_dir.mkdir(exist_ok=True)
+        rule_files: list[Path] = []
+        for device in devices:
+            devpath: str = str(device)
+            rule_file: Path = (
+                rules_dir / f"90-udisks-inhibit-{devpath.replace('/', '_')}.rules"
+            )
+            with rule_file.open("w") as fd:
+                print(
+                    'SUBSYSTEM=="block", ENV{DEVNAME}=="'
+                    + devpath
+                    + '*", ENV{UDISKS_IGNORE}="1"',
+                    file=fd,
+                )
+                fd.flush()
+                os.fsync(fd.fileno())
+            rule_files.append(rule_file)
+        run(["udevadm", "control", "--reload"])
+        run(["udevadm", "trigger", "--settle", "--subsystem-match=block"])
+
+        yield None
+    except Exception as ex:
+        log.fatal(ex)
+    finally:
+        for rule_file in rule_files:
+            rule_file.unlink(missing_ok=True)
+        run(["udevadm", "control", "--reload"], check=False)
+        run(["udevadm", "trigger", "--settle", "--subsystem-match=block"], check=False)
+
+
 @API.register
 def list_possible_keymaps() -> list[str]:
     cmd = nix_build(["nixpkgs#kbd"])
@@ -95,8 +150,11 @@ def flash_machine(
     dry_run: bool,
     write_efi_boot_entries: bool,
     debug: bool,
+    no_udev: bool = False,
     extra_args: list[str] | None = None,
 ) -> None:
+    devices = [Path(device) for device in disks.values()]
+    with pause_automounting(devices, no_udev):
         if extra_args is None:
             extra_args = []
         system_config_nix: dict[str, Any] = {}
@@ -201,6 +259,7 @@ class FlashOptions:
     mode: str
     write_efi_boot_entries: bool
     nix_options: list[str]
+    no_udev: bool
     system_config: SystemConfig
 
 
@@ -236,6 +295,7 @@ def flash_command(args: argparse.Namespace) -> None:
             wifi_settings=None,
         ),
         write_efi_boot_entries=args.write_efi_boot_entries,
+        no_udev=args.no_udev,
         nix_options=args.option,
     )
 
@@ -274,6 +334,7 @@ def flash_command(args: argparse.Namespace) -> None:
         dry_run=opts.dry_run,
         debug=opts.debug,
         write_efi_boot_entries=opts.write_efi_boot_entries,
+        no_udev=opts.no_udev,
         extra_args=opts.nix_options,
     )
 
@@ -343,6 +404,12 @@ def register_parser(parser: argparse.ArgumentParser) -> None:
         default=False,
         action="store_true",
     )
+    parser.add_argument(
+        "--no-udev",
+        help="Disable udev rules to block automounting",
+        default=False,
+        action="store_true",
+    )
     parser.add_argument(
         "--keymap",
         type=str,