s/bash/sh for all new *-lib.sh

modules.d/40network/net-lib.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 get_ip() {
     local iface="$1" ip=""

modules.d/45url-lib/url-lib.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # url-lib.sh - functions for handling URLs (file fetching etc.)
 #
 # Authors:

modules.d/99img-lib/img-lib.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 # img-lib.sh: utilities for dealing with archives and filesystem images.
 #
 # TODO: identify/unpack rpm, deb?