httpd: Could not reliably determine the server’s fully qualified domain name, using 127.0.0.1 for ServerName

I tried to restart my Apache server on CentOS 5.0 and got this message:

httpd: Could not reliably determine the server’s fully qualified domain name, using 127.0.0.1 for ServerName

Here is the /etc/hosts file:

127.0.0.1    server4-245    server4-245.com    localhost.localdomain localhost
::1        localhost6.localdomain6 localhost6

Here is the /etc/sysconfig/network file:

NETWORKING=yes
NETWORKING_IPV6=no
HOSTNAME=server4-245

I also have this in the Apache httpd.conf file:

ServerName localhost

However, I still get the first error message when I restart Apache.

Answer

Your hosts file does not include a valid FQDN, nor is localhost an FQDN. An FQDN must include a hostname part, as well as a domain name part. For example, the following is a valid FQDN:

host.server4-245.com

Choose an FQDN and include it both in your /etc/hosts file on both the IPv4 and IPv6 addresses you are using (in your case, localhost or 127.0.0.1), and change your ServerName in your httpd configuration to match.

/etc/hosts:

127.0.0.1    localhost.localdomain localhost host.server4-245.com
::1          localhost.localdomain localhost host.server4-245.com

httpd.conf:

ServerName host.server4-245.com