simplify nsswitch finalize script

- remove overbaring debugging
- don't print exceptions or handle exceptions when they are meant to be
fatal
- don't open the file multiple times
- don't check uid, it's inconsequental because we really only need a
writable file

mkosi.finalize.d/10-modify-nsswitch.py.chroot

@@ -6,54 +6,21 @@
 import os
 import sys
 
-def modify_nsswitch():
-    path = "/etc/nsswitch.conf"
-
-    print(f"Checking {path}...")  # Debug line
-
-    # Read the file
-    try:
-        with open(path, "r") as file:
-            lines = file.readlines()
-    except Exception as e:
-        print(f"Error reading {path}: {e}", file=sys.stderr)
-        raise  # Re-raise the exception
-
-    modified = False
-
-    # Process each line
+def replace_lines_in_place(lines):
     for i, line in enumerate(lines):
-        print(f"Checking line: {line.strip()}")  # Debug line
-        if line.startswith("hosts:"):
-            if "mymachines" in line and "mdns_minimal" not in line:
-                lines[i] = line.replace("mymachines", "mymachines mdns_minimal [NOTFOUND=return]", 1)
-                modified = True
-                print("Added mdns_minimal after mymachines.")  # Debug line
-            elif "mymachines" not in line and "mdns_minimal" not in line:
-                lines[i] = line.replace("hosts:", "hosts: mdns_minimal [NOTFOUND=return] ", 1)
-                modified = True
-                print("Added mdns_minimal.")  # Debug line
-            break
+        if not line.startswith("hosts: mymachines resolve"):
+            continue
 
-    if not modified:
-        raise RuntimeError("Expected modification but no changes were made.")
+        lines[i] = line.replace("mymachines", "mymachines mdns_minimal [NOTFOUND=return]", 1)
+        return
+    raise RuntimeError("Expected modification but no changes were made.")
 
-    # Write back the modified file
-    try:
-        with open(path, "w") as file:
-            file.writelines(lines)
-        print("Updated /etc/nsswitch.conf")
-    except Exception as e:
-        print(f"Error writing to {path}: {e}", file=sys.stderr)
-        raise  # Re-raise the exception
+def modify_nsswitch():
+    with open("/etc/nsswitch.conf", "r+") as file:
+        lines = file.readlines()
+        replace_lines_in_place(lines)
+        file.seek(0)
+        file.writelines(lines)
 
 if __name__ == "__main__":
-    if os.geteuid() != 0:
-        print("This script must be run as root.", file=sys.stderr)
-        sys.exit(1)
-
-    try:
-        modify_nsswitch()
-    except Exception as e:
-        print(f"Fatal error: {e}", file=sys.stderr)
-        sys.exit(1)
+    modify_nsswitch()