Add --debug-sandbox

This will help in debugging sandbox related issues. We run the sandbox
with strace and detach on execve() so we don't strace the command that
we're running.

mkosi/config.py

@@ -1547,6 +1547,7 @@ class Args:
     debug: bool
     debug_shell: bool
     debug_workspace: bool
+    debug_sandbox: bool
     pager: bool
     genkey_valid_days: str
     genkey_common_name: str
@@ -3775,6 +3776,12 @@ def create_argument_parser(chdir: bool = True) -> argparse.ArgumentParser:
         action="store_true",
         default=False,
     )
+    parser.add_argument(
+        "--debug-sandbox",
+        help="Run mkosi-sandbox with strace",
+        action="store_true",
+        default=False,
+    )
     parser.add_argument(
         "--no-pager",
         action="store_false",
@@ -4555,6 +4562,8 @@ def load_args(args: argparse.Namespace) -> Args:
         ARG_DEBUG.set(args.debug)
     if args.debug_shell:
         ARG_DEBUG_SHELL.set(args.debug_shell)
+    if args.debug_sandbox:
+        ARG_DEBUG_SANDBOX.set(args.debug_sandbox)
 
     return Args.from_namespace(args)
 

mkosi/log.py

@@ -11,6 +11,7 @@
 # This global should be initialized after parsing arguments
 ARG_DEBUG = contextvars.ContextVar("debug", default=False)
 ARG_DEBUG_SHELL = contextvars.ContextVar("debug-shell", default=False)
+ARG_DEBUG_SANDBOX = contextvars.ContextVar("debug-sandbox", default=False)
 LEVEL = 0
 
 

mkosi/resources/man/mkosi.1.md

@@ -234,16 +234,19 @@ Those settings cannot be configured in the configuration files.
     for in this directory, hence using this option is an effective way to
     build a project located in a specific directory.
 
-`--debug=`
+`--debug`
 :   Enable additional debugging output.
 
 `--debug-shell`
 :   When executing a command in the image fails, mkosi will start an interactive
     shell in the image allowing further debugging.
 
-`--debug-workspace=`
+`--debug-workspace`
 :   When an error occurs, the workspace directory will not be deleted.
 
+`--debug-sandbox`
+:   Run `mkosi-sandbox` with `strace`.
+
 `--version`
 :   Show package version.
 

mkosi/run.py

@@ -21,7 +21,7 @@
 from typing import Any, Callable, NoReturn, Optional, Protocol
 
 import mkosi.sandbox
-from mkosi.log import ARG_DEBUG, ARG_DEBUG_SHELL, die
+from mkosi.log import ARG_DEBUG, ARG_DEBUG_SHELL, ARG_DEBUG_SANDBOX, die
 from mkosi.sandbox import acquire_privileges, joinpath, umask
 from mkosi.types import _FILE, CompletedProcess, PathString, Popen
 from mkosi.util import current_home_dir, flatten, one_zero
@@ -485,6 +485,7 @@ def sandbox_cmd(
 
     cmdline: list[PathString] = [
         *setup,
+        *(["strace", "--detach-on=execve"] if ARG_DEBUG_SANDBOX.get() else []),
         sys.executable, "-SI", mkosi.sandbox.__file__,
         "--proc", "/proc",
         # We mounted a subdirectory of TMPDIR to /var/tmp so we unset TMPDIR so that /tmp or /var/tmp are