scripts: Add convenience script to disable wall messages from syslog.

If the server is being used as a syslog server, then it is prone to
receiving emergency messages from the outside that can trigger wall
messages to go to all the system terminals. This won't impact BBS
nodes at all, but can be bothersome to the sysop. Add a script to
disable this, for convenience.

scripts/disablewall.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# Disable broadcast wall messages from syslog to avoid interfering with terminal sessions
+# Won't affect BBS nodes either way, but could be annoying to the sysop if not done
+# Recommended if syslog is enabled on this server
+
+# Test before
+logger -p local0.emerg "This is a test, not a real emergency"
+
+# Disable default emergency rule: *.emerg :omusrmsg:*
+sed -e '/*.emerg/ s/^#*/#/' -i /etc/rsyslog.conf
+
+# Disable forwarding to wall for journald
+sed -i 's/#ForwardToWall=yes/ForwardToWall=no/' /etc/systemd/journald.conf
+
+# Reload
+systemctl force-reload systemd-journald
+systemctl restart rsyslog
+
+# Test again: this should no longer generate a broadcast
+logger -p local0.emerg "This is a test, not a real emergency"