improve update of /etc/hosts

 * use 127.0.1.1 under debian (since it's the default there)
 * also set the IPv6 loopback address (::1) since some tools tries to
   AAAA resolve the hostname (for example sendmail)
 * ensure proper /etc/hosts format through postinst-script (hostname as
   last entry)

debian/qubes-core-agent.postinst

@@ -0,0 +1,15 @@
+# ensure that hostname resolves to 127.0.1.1 resp. ::1 and that /etc/hosts is
+# in the form expected by qubes-sysinit.sh
+for ip in '127\.0\.1\.1' '::1'; do
+    if grep -q "^${ip}\(\s\|$\)" /etc/hosts; then
+        sed -i "/^${ip}\s/,+0s/\(\s`hostname`\)\+\(\s\|$\)/\2/g" /etc/hosts
+        sed -i "s/^${ip}\(\s\|$\).*$/\0 `hostname`/" /etc/hosts
+    else
+        echo "${ip} `hostname`" >> /etc/hosts
+    fi
+done
+# remove hostname from 127.0.0.1 line (in debian the hostname is by default
+# resolved to 127.0.1.1)
+sed -i "/^127\.0\.0\.1\s/,+0s/\(\s`hostname`\)\+\(\s\|$\)/\2/g" /etc/hosts
+
+#DEBHELPER#

rpm_spec/core-vm.spec

@@ -210,6 +210,17 @@ if ! grep -q localhost /etc/hosts; then
 EOF
 fi
 
+# ensure that hostname resolves to 127.0.0.1 resp. ::1 and that /etc/hosts is
+# in the form expected by qubes-sysinit.sh
+for ip in '127\.0\.0\.1' '::1'; do
+    if grep -q "^${ip}\(\s\|$\)" /etc/hosts; then
+        sed -i "/^${ip}\s/,+0s/\(\s`hostname`\)\+\(\s\|$\)/\2/g" /etc/hosts
+        sed -i "s/^${ip}\(\s\|$\).*$/\0 `hostname`/" /etc/hosts
+    else
+        echo "${ip} `hostname`" >> /etc/hosts
+    fi
+done
+
 if [ "$1" !=  1 ] ; then
 # do the rest of %post thing only when updating for the first time...
 exit 0

vm-systemd/qubes-sysinit.sh

@@ -62,7 +62,13 @@ done
 name=`$XS_READ name`
 if [ -n "$name" ]; then
     hostname $name
-    sed -i "s/^\(127\.0\.0\.1 .*\) \($name \)\?\(.*\)/\1\2 $name/" /etc/hosts
+    if [ -e /etc/debian_version ]; then
+        ipv4_localhost_re="127\.0\.1\.1"
+    else
+        ipv4_localhost_re="127\.0\.0\.1"
+    fi
+    sed -i "s/^\($ipv4_localhost_re\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
+    sed -i "s/^\(::1\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
 fi
 
 timezone=`$XS_READ qubes-timezone 2> /dev/null`