How to Fix Apache AH00094: Command Line Exceeded Limit in 2.4.60+
Quick Fix Summary
TL;DRReduce the total length of arguments passed to Apache's main process by consolidating or removing directives in your configuration.
Apache 2.4.60+ enforces the system's ARG_MAX limit on the combined length of all command-line arguments passed during startup. This error occurs when the total length of configuration directives, environment variables, and other arguments exceeds this hard OS limit, preventing the server from starting.
Diagnosis & Causes
Recovery Steps
Step 1: Diagnose the Argument Length
First, determine the current total argument length being passed to Apache. Use the `getconf` command to find your system's ARG_MAX limit and a script to estimate Apache's usage.
# Check your system's ARG_MAX limit
getconf ARG_MAX
# Example output: 2097152 (2MB on many Linux systems)
# For a rough estimate, sum the character count of key config lines.
# Use `truncate` to simulate the error and find the breaking point:
sudo /usr/sbin/apache2 -t 2>&1 | grep -i "command line"Step 2: Consolidate Configuration with IncludeOptional
Replace bulky `Include` directives with `IncludeOptional`. This directive is parsed later in the startup sequence and its contents are not counted towards the initial command-line argument limit.
# CHANGE THIS in your main apache2.conf or httpd.conf:
# Include /etc/apache2/sites-enabled/*.conf
# TO THIS:
IncludeOptional /etc/apache2/sites-enabled/*.confStep 3: Move Environment Variables to a File
Long `SetEnv` or `PassEnv` directives are major contributors. Move them to an environment file and load it using `PassEnv` with a single filename.
# 1. Create an environment file: /etc/apache2/env.vars
APACHE_LONG_VAR_1=very_long_value_here
APACHE_LONG_VAR_2=another_extremely_long_string
# 2. In your Apache config, replace many SetEnv lines with:
PassEnv APACHE_LONG_VAR_1 APACHE_LONG_VAR_2
# Or, source it in your systemd service file with EnvironmentFile=Step 4: Optimize Virtual Host Configuration
Simplify VirtualHost blocks. Use shorter domain names in ServerName/ServerAlias and consider breaking up massive virtual host files into smaller, modular includes.
# BEFORE: Long, complex VirtualHost
<VirtualHost *:80>
ServerName very-long-subdomain-name.example.com
ServerAlias another-very-long-alias.example.com www.another-very-long-alias.example.com
# ... many more long directives ...
</VirtualHost>
# AFTER: Simplified core, move rules to an included file.
<VirtualHost *:80>
ServerName short.example.com
IncludeOptional /etc/apache2/vhosts/short-example-rules.conf
</VirtualHost>Step 5: Modify Systemd Service Limits (Linux)
If consolidation isn't enough, you can override the systemd service to increase the argument limit for the Apache process specifically. This is a last resort.
# Create a systemd override directory and file
sudo systemctl edit apache2.service
# Add the following to the editor, then save and exit:
[Service]
LimitARG_MAX=infinity
# Reload systemd and restart Apache
sudo systemctl daemon-reload
sudo systemctl restart apache2Step 6: Verify and Restart
After applying changes, test the configuration syntax and restart Apache. Monitor logs to confirm a clean startup.
# Test configuration syntax
sudo apachectl configtest
# If syntax is OK, restart Apache
sudo systemctl restart apache2
# Check for the AH00094 error in the logs
sudo tail -f /var/log/apache2/error.log | grep AH00094Architect's Pro Tip
"The error often appears after adding SSL certificates with long paths or many SANs. Use symbolic links (`ln -s`) in `/etc/ssl/certs/` to create shorter paths referenced in your SSLCertificateFile directive."
Frequently Asked Questions
Why did this error start appearing after upgrading to Apache 2.4.60?
Apache 2.4.60 introduced stricter enforcement of the POSIX-mandated ARG_MAX limit for security and stability. Earlier versions might have silently truncated or behaved unpredictably with excessively long command lines.
Can I just increase the ARG_MAX limit on my system?
ARG_MAX is a kernel-level constant and cannot be changed at runtime for a single process. The systemd override method (LimitARG_MAX) is the only safe 'increase,' as it tells the kernel to ignore the limit for that specific service.
Does this affect Apache running on Windows?
No. The AH00094 error and ARG_MAX limit are specific to Unix-like operating systems (Linux, BSD, macOS). Windows has different constraints for command-line argument length.