config: find required programs every time pmbootstrap is run (MR 2475)

On debian systems in particular special handling is needed for
/usr/sbin. Let's do this once and then provide the host deps we use in a
nice accessible dictionary.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>
Tweaked-by: Oliver Smith <ollieparanoid@postmarketos.org>

pmb/__init__.py

@@ -14,7 +14,7 @@ if TYPE_CHECKING:
 
 from . import config
 from . import parse
-from .config import init as config_init
+from .config import init as config_init, require_programs
 from .helpers import frontend
 from .helpers import logging
 from .helpers import mount
@@ -76,6 +76,9 @@ def main() -> int:
         if not args.as_root and os.geteuid() == 0:
             raise RuntimeError("Do not run pmbootstrap as root!")
 
+        # Check for required programs (and find their absolute paths)
+        require_programs()
+
         # Initialize or require config
         if args.action == "init":
             config_init.frontend(args)

pmb/config/__init__.py

@@ -14,6 +14,7 @@ from collections.abc import Sequence
 from pmb.config.file import load, save, serialize
 from pmb.config.sudo import which_sudo
 from pmb.config.other import is_systemd_selected
+from .init import require_programs
 from . import workdir
 
 
@@ -58,14 +59,16 @@ ondev_min_version = "0.2.0"
 # Programs that pmbootstrap expects to be available from the host system. Keep
 # in sync with README.md, and try to keep the list as small as possible. The
 # idea is to run almost everything in Alpine chroots.
-required_programs = [
-    "git",
-    "kpartx",
-    "losetup",
-    "openssl",
-    "ps",
-    "tar",
-]
+required_programs: dict[str, str] = {
+    "git": "",
+    "kpartx": "",
+    "losetup": "",
+    "openssl": "",
+    "ps": "",
+    "tar": "",
+    "chroot": "",
+    "sh": "",
+}
 
 
 def sudo(cmd: Sequence[PathString]) -> Sequence[PathString]:

pmb/config/init.py

@@ -36,11 +36,14 @@ import pmb.parse._apkbuild
 
 def require_programs() -> None:
     missing = []
-    for program in pmb.config.required_programs:
+    for program in pmb.config.required_programs.keys():
         # Debian: some programs are in /usr/sbin, which is not in PATH
         # unless using sudo
-        if not shutil.which(program) and not os.path.exists(os.path.join("/usr/sbin", program)):
+        prog = shutil.which(program, path=pmb.config.host_path)
+        if not prog:
             missing.append(program)
+        else:
+            pmb.config.required_programs[program] = prog
 
     losetup_missing_json = False
 
@@ -694,8 +697,6 @@ def ask_for_locale(current_locale: str) -> str:
 
 
 def frontend(args: PmbArgs) -> None:
-    require_programs()
-
     # Work folder (needs to be first, so we can create chroots early)
     config = get_context().config