Introduction
An Apache AH00558: Could not reliably determine the server's fully qualified domain name
message is generated when Apache is not configured with a global ServerName
directive. The message is mainly for informational purposes, and an AH00558 error will not prevent Apache from running correctly.
In this tutorial you will learn how to detect an AH00558 message using the methods described in the How to Troubleshoot Common Apache Errors tutorial at the beginning of this series. You will also learn how to set a ServerName
directive to resolve the message.
If you have already determined that your Apache server is affected by an AH00558 message and you would like to skip the troubleshooting steps, the Setting a Global ServerName
Directive step at the end of this tutorial explains how to resolve the message.
Troubleshooting Using systemctl
The first step when you are troubleshooting an AH00558: Could not reliably determine the server's fully qualified domain name
message is to check Apache’s status using systemctl
. The output from systemctl
will in many cases contain all the information that you need to resolve the message.
On Ubuntu and Debian-derived Linux distributions, run the following to check Apache’s status:
- sudo systemctl status apache2.service -l --no-pager
On CentOS Fedora, and RedHat-derived systems, use this command to examine Apache’s status:
- sudo systemctl status httpd.service -l --no-pager
The -l
flag will ensure that systemctl
outputs the entire contents of a line, instead of substituting in ellipses (…
) for long lines. The --no-pager
flag will output the entire log to your screen without invoking a tool like less
that only shows a screen of content at a time.
You should receive output that is similar to the following:
Output● apache2.service - The Apache HTTP Server
Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
Drop-In: /lib/systemd/system/apache2.service.d
└─apache2-systemd.conf
Active: active (running) since Wed 2020-07-29 14:30:03 UTC; 33min ago
Process: 34 ExecStart=/usr/sbin/apachectl start (code=exited, status=0/SUCCESS)
Main PID: 46 (apache2)
Tasks: 55 (limit: 2344)
CGroup: /system.slice/apache2.service
├─46 /usr/sbin/apache2 -k start
├─47 /usr/sbin/apache2 -k start
└─48 /usr/sbin/apache2 -k start
Jul 29 14:30:03 68e2cf19f3f1 systemd[1]: Starting The Apache HTTP Server...
Jul 29 14:30:03 68e2cf19f3f1 apachectl[34]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
Jul 29 14:30:03 68e2cf19f3f1 systemd[1]: Started The Apache HTTP Server.
The highlighted line that contains the AH00558 message is the important one. Essentially, it informs you that Apache couldn’t find a valid ServerName
directive in its configuration file, so it will use the first IP address it detects. In this example, it’s the server’s public IP address: 172.17.02
. If you are troubleshooting an AH00558 message, the IP address that is detected may be different, or it may be a human readable DNS name.
If your systemctl
output contains an auto-detected value of any IP address or hostname, skip to the last section of this tutorial, Setting a Global ServerName
Directive to resolve the issue. In that section you will configure Apache with a safe default ServerName
value using the IP address for localhost
: 127.0.0.1
.
If your systemctl
output does not indicate a value that you can use for the ServerName
directive, the next section of this tutorial explains how to examine the systemd
logs using journalctl
to locate an AH00558 message.
Troubleshooting Using journalctl
To examine the systemd
logs for Apache you will use the journalctl
command. When invoking journalctl
, there are two specific flags that will help you locate specific messages if there is a large volume of log entries.
The first flag that you will add to the journalctl
invocation is the --since today
flag. It will limit the output of the command to log entries beginning at 00:00:00 of the current day only. Using this option will help restrict the volume of log entries that you need to examine when checking for errors.
The second flag that you will use is the same --no-pager
option that you used with systemctl
, which will output the entire log to your screen at once.
On Ubuntu and Debian-derived systems, run the following command:
- sudo journalctl -u apache2.service --since today --no-pager
On CentOS, Fedora, and RedHat-derived systems, use this command to inspect the logs:
- sudo journalctl -u httpd.service --since today --no-pager
If your Apache server is generating an AH00558 message, look through the journalctl
command output for lines like the following:
Output-- Logs begin at Wed 2020-07-29 14:30:02 UTC, end at Wed 2020-07-29 14:45:03 UTC. --
. . .
Jul 29 14:30:03 68e2cf19f3f1 systemd[1]: Starting The Apache HTTP Server...
Jul 29 14:30:03 68e2cf19f3f1 apachectl[34]: AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
Jul 29 14:30:03 68e2cf19f3f1 systemd[1]: Started The Apache HTTP Server.
The second line of output is the AH00558 message. The line includes the server’s public IP address, which is the address that Apache automatically detects and sets as a default at runtime. With this message as confirmation of an AH00558 error, you can proceed to the Setting a Global ServerName
Directive to resolve the issue.
Otherwise, the next section explains how to diagnose an AH00558 error message using the apachectl
command.
Troubleshooting using apachectl
An AH00558: Could not reliably determine the server's fully qualified domain name
error can be detected using Apache’s apachectl
utility. With apachectl
you can catch messages like these before reloading or restarting Apache, and you can avoid having to search through systemctl
and journalctl
logs to locate errors.
To check your Apache configuration for an AH00558 message, run the following command:
- sudo apachectl configtest
You should receive output like the following if your server is affected by an AH00558 error message:
OutputAH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.2. Set the 'ServerName' directive globally to suppress this message
Syntax OK
As with the previous sections in this tutorial that used systemctl
and journalctl
to locate AH00558 messages, the line that contains the AH00558 message, highlighted in the previous example, is the important one. Again note that the IP address 172.17.0.2
in this example may be different on your server.
The next section of this tutorial explains how to set the ServerName
directive to resolve AH00558 error messages.
Setting a Global ServerName
Directive
To resolve an AH00558: Could not reliably determine the server's fully qualified domain name
error message, you will need to add a ServerName
directive to your Apache configuration. Apache uses the ServerName
directive to map incoming HTTP requests to an IP address or DNS hostname using VirtualHost
directives in order to handle requests for multiple sites using a single server.
The error message notes that a global ServerName
directive should also be set. Doing so will ensure that Apache can gracefully handle incoming requests that do not map to a VirtualHost
without generating additional errors.
For maximum compatibility with various Apache configurations, use the value of 127.0.0.1
for your global ServerName
directive. You can use a different IP address or DNS name that corresponds to your server’s configuration if you need to, but it is safest to use 127.0.0.1
.
On Ubuntu and Debian-derived systems, open the /etc/apache2/apache2.conf
file with root privileges using nano
or your preferred text editor:
- sudo nano /etc/apache2/apache2.conf
Add a line containing ServerName 127.0.0.1
to the end of the file:
. . .
# Include the virtual host configurations:
IncludeOptional sites-enabled/*.conf
# vim: syntax=apache ts=4 sw=4 sts=4 sr noet
ServerName 127.0.0.1
On CentOS, Fedora, and RedHat-derived systems, open the /etc/httpd/conf/httpd.conf
file with root privileges using nano
or your preferred text editor:
- sudo nano /etc/httpd/conf/httpd.conf
Add the ServerName 127.0.0.1
line to the end of the file:
. . .
# Supplemental configuration
#
# Load config files in the "/etc/httpd/conf.d" directory, if any.
IncludeOptional conf.d/*.conf
ServerName 127.0.0.1
Save and close the file when you are finished. If you used nano
, do so by pressing CTRL + X
, Y
, and then ENTER
.
Once you have added the ServerName
directive to your configuration, run apachectl
to test that the configuration is valid.
- sudo apachectl configtest
A successful apachectl configtest
invocation should result in output like this:
OutputSyntax OK
You can now restart Apache using the appropriate systemctl restart
command for your Linux distribution.
On Ubuntu and Debian-derived systems, run the following:
- sudo systemctl restart apache2.service
On CentOS, Fedora, and RedHat-derived systems use this command to restart Apache:
- sudo systemctl restart httpd.service
After you restart Apache, the AH00558 error message will no longer appear in your logs. You can confirm the messages are silenced by running any of the three systemctl
, journalctl
, or apachectl
commands that are demonstrated in this tutorial.
Conclusion
In this tutorial you learned about AH00558: Could not reliably determine the server's fully qualified domain name
error messages. While these messages do not prevent Apache from running, they can be resolved by setting a global ServerName
directive.
You learned how to search for AH00558 error messages using the systemctl
, journalctl
, and apachectl
commands. Finally, you learned how to edit your Apache configuration on various Linux distributions to silence the messages.
If you would like to learn more about how Apache uses ServerName
directives, the Apache documentation about Name-Based Virtual Hosts explains the directive in more detail.
Originally posted on DigitalOcean Community Tutorials
Author: Jamon Camisso
So then why when I try to access my https://matthewdykstra.com it cannot open page? and when I check the logs for the server I still see the message about the qualified server name