Knowledge Base

Unable to start Apache: Unable to find IPv4 address of server.example.com

Symptoms

Apache on Plesk server cannot be started manually or Apache is not started automatically after a server reboot. One of the following error messages appears in the Apache error log file:
- On CentOS/RHEL-based distributions: /var/log/httpd/error_log
- On Debian/Ubuntu-based distributions: /var/log/apache2/error.log
```
(EAI 2)Name or service not known: AH01564: unable to find IPv4 address of "server.example.com"
AH00016: Configuration Failed
```
```
(EAI 3)Temporary failure in name resolution: AH01564: unable to find IPv4 address of "ip-203-0-113-2"
AH00016: Configuration Failed
```

The following email notification might be sent to Plesk administrator:

Unable to generate the web server configuration file on the host <server.example.com> because of the following errors: Template_Exception: Can not restart web server: file: /opt/psa/admin/plib/Service/Driver/Web/Server/Apache.php line: 109 code: 0

Unable to generate the web server configuration file on the host <server-hostname> because of the following errors:
Template_Exception: Can not restart web server: Apache is down, start it instead of graceful Apache is down, start it instead of graceful

Cause

There is no IPv4 specified in the /etc/hosts file for the server name configured in /etc/hostname file.

Resolution

Log into Plesk
Navigate to Tools & Settings > Server Settings in “Full hostname” set the server hostname and click “OK” button. Note that the server name should include domain part, for example: server.example.com

Command line

Connect to the server via SSH
Edit the file /etc/hosts and add valid <IPv4 hostname> configuration:

Note: If the system has configured ‘manage_etc_hosts‘ as True, check this KB article.
```
203.0.113.2 server.example.com
```
- Server hostname can be edited in the file /etc/hostname or it can be found with the command hostname
Reboot the server
Verify that Apache has been started:
- On CentOS/RHEL-based distributions:
  
  # service httpd status
- On Debian/Ubuntu-based distributions:
  
  # service apache2 status