utils: T8541: add write-config-file-value helper

Introduce src/helpers/write-config-file-value.py to patch a saved config.boot
from scripts by writing a quoted CLI path with an optional value (omit --value
to create a valueless node).

Extend vyos.utils.config.write_saved_value() to safely update saved configs:
create missing parent nodes before tagging (ConfigTree.set_tag requires nodes
to exist) and then write the requested value/valueless leaf back to disk.

Remove the legacy serial console activation script which is now replaced by the
helper-based approach. The helper is run once during ISO Image assembly and will
inject the approprate serial console defintiions into config.boot.default.

1 files changed, 48 insertions, 0 deletions

diff --git a/src/helpers/write-config-file-value.py b/src/helpers/write-config-file-value.py
new file mode 100644
index 000000000..f3993223c
--- /dev/null
+++ b/src/helpers/write-config-file-value.py
@@ -0,0 +1,48 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) VyOS Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from argparse import ArgumentParser
+from shlex import split as shlex_split
+
+from vyos.utils.config import write_saved_value
+
+def _split_quoted(s: str) -> list[str]:
+    parts = shlex_split(s)
+    if not parts:
+        raise ValueError('empty string')
+    return parts
+
+if __name__ == '__main__':
+    parser = ArgumentParser()
+    parser.add_argument(
+        '--path',
+        required=True,
+        help='Quoted CLI path, e.g. "system console device ttyS1 speed"',
+    )
+    parser.add_argument(
+        '--value',
+        required=False,
+        help='Value for the node, e.g. "9600". If omitted, creates a valueless node.',
+    )
+    parser.add_argument(
+        '--config-file',
+        required=True,
+        help=f'Path to saved config.boot',
+    )
+    args = parser.parse_args()
+
+    path = _split_quoted(args.path)
+    write_saved_value(path, value=args.value, config_path=args.config_file)