Trying to bind apache2 to localhost only, running Ubuntu 12.04.3 LTS on OpenVZ VPS. It fails on me (see /var/log/apache2/error.log). Default configuration is:
# cat /etc/hosts fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters 127.0.0.1 localhost.localdomain localhost # Auto-generated hostname. Please do not remove this comment. <some-ext-ipv6-address> <some-hostname> ::1 localhost ip6-localhost ip6-loopback # netstat -lntup tcp6 0 0 :::80 :::* LISTEN 623/apache2 I change Listen 80 to Listen 172.0.0.1:80 in /etc/apache2/ports.conf.
Apache2 errors out. There is no other service listening on port 80, also there is no other (conflicting) Listen declaration, just the default ports.conf apache2 ships with + the single change described.
# cat /var/log/apache2/error.log apache2: Could not reliably determine the server's fully qualified domain name, using <some-ext-ipv6-address> for ServerName (99)Cannot assign requested address: make_sock: could not bind to address 172.0.0.1:80 no listening sockets available, shutting down Unable to open logs 
