etc: add NetworkManager-resolv.conf-restore.bash

etc/NetworkManager-resolv.conf-restore.bash

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -x
+
+# I learned that not only systemd-resolved does this, but NetworkManager as
+# well. I think it's even less likely I use this than the systemd-resolved
+# one, but anyway
+
+# I know there are old versions that used something else, but I don't remember
+# that name and they are ancient.
+if ! hash nmcli 2>/dev/null; then
+	echo "You don't seem to have NetworkManager (or nmcli) installed." 1>&2
+	exit 1
+fi
+
+# Require root or exit
+if [ "$(id -u)" != "0" ]; then
+	echo "This script requires root." 1>&2
+	exit 1
+fi
+
+# It's pointless to make a dead symlink as it must be running
+systemctl enable --now NetworkManager.service
+
+# In case I am behind the /etc/resolv.conf, it's immutable and read-only,
+# which won't allow it to be rewritten.
+chattr -V -i /etc/resolv.conf
+chmod -v +w /etc/resolv.conf
+
+# It must be removed if it's not a symlink
+rm -v /etc/resolv.conf
+
+# and finally making the symlink
+ln -sfv /var/run/NetworkManager/resolv.conf /etc/resolv.conf
+
+# Let's just see it's ok
+ls -l /etc/resolv.conf
+cat /etc/resolv.conf
+
+set +x