Add /etc/hosts and hostname and FQDN setting.

diff --git a/all_new_2018/set_hostname_and_fqdn.sh b/all_new_2018/set_hostname_and_fqdn.sh
new file mode 100755 (executable)
index 0000000..f39a359
--- /dev/null
+++ b/all_new_2018/set_hostname_and_fqdn.sh
@@ -0,0 +1,46 @@
+#!/bin/sh
+# Sets hostname and optionally FQDN.
+#
+# Calls hostname, writes to /etc/hostname and /etc/hosts. For /etc/hosts
+# writing follows recommendations from Debian manual at
+# <https://www.debian.org/doc/manuals/debian-reference/ch05.en.html>
+# (section "The hostname resolution") on how to map hostname and possibly
+# FQDN to a permanent IP if present (we assume here any non-private IP
+# and non-loopback IP returned by hostname -I to fulfill that criterion
+# on our systems) or to 127.0.1.1 if not. On the reasoning for separating
+# localhost and hostname mapping to different IPs, see
+# <https://unix.stackexchange.com/a/13087>.
+set -e
+
+hostname="$1"
+fqdn="$2"
+if [ "${hostname}" = "" ]; then
+    echo "Need hostname as argument."
+    false
+fi
+
+echo "${hostname}" > /etc/hostname
+hostname "${hostname}"
+
+final_ip="127.0.1.1"
+for ip in $(hostname -I); do
+    range_1=$(echo "${ip}" | cut -d "." -f 1)
+    range_2=$(echo "${ip}" | cut -d "." -f 2)
+    if [ "${range_1}" -eq 127 ]; then
+        continue
+    elif [ "${range_1}" -eq 10 ]; then
+        continue
+    elif [ "${range_1}" -eq 172 ]; then
+        if [ "${range_2}" -ge 16 ] && [ "${range_2}" -le 31 ]; then
+            continue
+        fi
+    elif [ "${range_1}" -eq 192 ]; then
+        if [ "${range_2}" -eq 168 ]; then
+            continue
+        fi
+    fi
+    echo 'SETTING' $ip
+    final_ip="${ip}"
+done
+echo "127.0.0.1 localhost.localdomain localhost" > /etc/hosts
+echo "${final_ip} ${fqdn} ${hostname}" >> /etc/hosts