Apache Error Messages Checklist
Error logs are an effective and powerful tool for managing and troubleshooting your Apache web server.
The problem is that these messages are often cryptic and hard to understand. To help you understand the information these messages provide, we have compiled the following list of Apache errors with a simple explanation of what they mean.
* If you haven’t read our power guide: “Apache Error Log & Apache Access Log: Analyzing + Troubleshooting Apache” we recommend you to do so right now.
| Error | Meaning |
| AcceptExFailed | A Microsoft Windows networking error triggered by firewall, antivirus, VPN, or other networking software interfering with the correct operation of the Windows networking APIs. |
| DirectoryAsScript | A request attempted to run a directory as a script. The cause of this problem when Apache is configured to run with ScriptAlias. As a result, when a request is received for for a directory path, the resources in that location are considered executable. |
| ClientDeniedByServerConfiguration | Client request does not have sufficient permissions as defined by the Apache server’s configuration. Consequently, the request is denied access to resources or data. |
| CouldNotDetermineServerName | The request could not determine the server’s fully qualified domain name. This warning usually occurs when launching the Apache httpd process. At this time, the service is unable to determine the name used to access the server by external parties. |
| CouldNotBindToAddress | Apache was unable to bind to the IP address 0.0.0.0:80. This can be the result of three possible causes.
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| ExecFormatError | Indicates that a script or configuration file was using an incorrect format, and apache was unable to execute a script or access a resource. |
| Favicon | Apache is unable to locate and display the site’s favicon.ico file from the URL provided. |
| SendfileNotImplemented | Apache HTTP Server tries to use the sendfile function to call the operating system’s file management system. By delegating file system operations to the host’s operating systems, Apache can receive and deliver files to and from the network efficiently, and handle more simultaneous requests. When this mechanism fails to work, this error message is generated. |
| InvalidArgumentCoreOutputFilter | Apache HTTP Server tries to use the sendfile to call the operating system’s file management system. When Apache is unable to access sendfile, this error is generated. Since dynamically generated content does not use sendfile, this problem is only experienced by static files. |
| InvalidCommandAuthDigestFile | This error occurs when Apache is configured to use AuthDigestFile, instead of AuthUserFile. Note this only applies to Apache 2.2 and earlier Apache versions. |
| InvalidMethodHTTPSonHTTP | Indicates that you you are attempting to connect to a non-HTTPS website site using the HTTPS protocol. |
| VirtualHostsMixingPorts | An error that occurs when launching Apache as a result of the following configuration errors:
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| IPCExhaustion | The server has run out of available slots for inter-process communication. This occurs when a process crashes before cleaning up after itself. |
| HttpreadyAcceptFilter | This errors happens when the accf_http kernel module is not loaded. This module helps reduces CPU utilization required to handle incoming requests and reducing the size of files handled by Apache. This is achieved by delaying the processing of incoming HTTP requests until they have been buffered by the kernel. |
| 13PermissionDenied | A filesystem permissions problem that prevents Apache from accessing a file or directory. This problem originates in the host’s file system and is not the result of Apache configuration errors. For Apache 2.4, or higher these error codes and messages provide additional information.
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| PcfgOpenfile | Apache can use distributed configuration files (.htaccess) to provide access to different parts of the host’s file system. This error indicates that Apache is unable to locate the .htaccess file. In some cases, this error is triggered by file systems that return unexpected errors when accessing a directory. |
| PrematureEndOfScriptHeaders | The Common Gateway Interface (CGI) script failed to write one or more HTTP response headers to a log file. This usually indicates that a CGI script simply crashed before it could generate a response. |
| ApGetScoreboardLb | Indicates that a child process did not have the correct permissions to access a file or resource. |
| NoProtocolHandlerForURL | The proxy assigned to handle the request was not assigned a valid protocol handler for the specified URL. |
| SSLSessionCache | Session Cache is not configured due to incomplete SSL directives in the base SSL virtual host configuration file. |
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