write uid map files manually if root

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "zenlib"
-version = "3.1.3"
+version = "3.1.4"
 authors = [
   { name="Desultory", email="[email protected]" },
 ]

src/zenlib/namespace/namespace.py

@@ -1,4 +1,4 @@
-from os import CLONE_NEWNS, CLONE_NEWUSER, getlogin, unshare
+from os import CLONE_NEWNS, CLONE_NEWUSER, getlogin, unshare, getuid
 from subprocess import CalledProcessError, run
 
 
@@ -19,11 +19,32 @@ def get_id_map(username=None, id_type="uid"):
     raise ValueError(f"User {username} not found in /etc/sub{id_type}")
 
 
+def write_id_map(id_type, pid, *args, failures=0):
+    if id_type not in ("uid", "gid"):
+        raise ValueError("id_type must be 'uid' or 'gid")
+
+    map_file = f"/proc/{pid}/uid_map" if id_type == "uid" else f"/proc/{pid}/gid_map"
+
+    # Get id, nsid, count tuples from args
+    map_contents = [f"{id} {nsid} {count}" for id, nsid, count in zip(*[iter(args)] * 3)]
+
+    try:
+        with open(map_file, "w") as f:
+            f.write("\n".join(map_contents))
+    except PermissionError as e:
+        if failures > 5:
+            raise e
+        new_id_map(id_type, pid, *args, failures=failures + 1)
+
 def new_id_map(id_type, pid, id, nsid, count=1, *args, failures=0):
     if id_type not in ("uid", "gid"):
         raise ValueError("id_type must be 'uid' or 'gid")
-    cmd_args = [f"new{id_type}map", str(pid), str(id), str(nsid), str(count), *map(str, args)]
+
+    if getuid() == 0:
+        return write_id_map(id_type, pid, id, nsid, count, *args)
+
     try:
+        cmd_args = [f"new{id_type}map", str(pid), str(id), str(nsid), str(count), *map(str, args)]
         return run(cmd_args, check=True, capture_output=True)
     except CalledProcessError as e:
         if failures > 5: