Apache HTTP Server Error Log

Logs errors, warnings, and diagnostic information

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Quick Facts

Default Path (Linux)

/var/log/apache2/error.log

Docker

stderr

Default Format

text

JSON Native

Rotation

logrotate

Log Example

Default format: Default Error Format

Example Log Entrylog

[Thu Dec 20 14:32:18.123456 2025] [core:error] [pid 1234:tid 5678] [client 192.168.1.50:54321] File does not exist: /var/www/html/missing.html

Structure:

[timestamp] [module:level] [pid tid] [client ip:port] message

Paths by Platform

Debian , Ubuntu

/var/log/apache2/error.log

RHEL / CentOS / Fedora

/var/log/httpd/error_log

Available Formats

Default Error Format

Default

Example:

[Thu Dec 20 14:32:18.123456 2025] [core:error] [pid 1234:tid 5678] [client 192.168.1.50:54321] File does not exist: /var/www/html/missing.html

Structure:

[timestamp] [module:level] [pid tid] [client ip:port] message

Fields Reference

Field	Type	Description	Example
`timestamp`	datetime	When the error occurred	`Thu Dec 20 14:32:18.123456 2025`
`module`	string	Apache module that generated the message	`core`
`level`	string	Log level	`error`
`pid`	integer	Process ID	`1234`
`tid`	integer	Thread ID	`5678`
`client`	string	Client IP and port	`192.168.1.50:54321`
`message`	string	Error message	`File does not exist: /var/www/html/missing.html`

Parsing Patterns

Regular Expressions

default:

^\[(?P<timestamp>[^\]]+)\] \[(?P<module>[^:]+):(?P<level>[^\]]+)\] \[pid (?P<pid>\d+):tid (?P<tid>\d+)\] (?:\[client (?P<client>[^\]]+)\] )?(?P<message>.*)$

Collector Configurations

logstashruby

1filter {
2  grok {
3    match => { "message" => "\[%{DATA:timestamp}\] \[%{WORD:module}:%{WORD:level}\] \[pid %{NUMBER:pid}:tid %{NUMBER:tid}\] (?:\[client %{DATA:client}\] )?%{GREEDYDATA:error_message}" }
4  }
5}

Configuration

Enable Logging

Directive:

ErrorLog /var/log/apache2/error.log

Use Cases

Error rate monitoring

Track error frequency

level

timestamp

Troubleshooting

Tested On

v2.4.58 on Ubuntu 24.04

admin - 2025-12-10

Last updated: 2025-12-15 by admin

1 contributor45 upvotes

Validated

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