When examining Apache's error.log, you'll frequently encounter entries like:

[mpm_prefork:notice] AH00163: Apache configured -- resuming normal operations
[mpm_prefork:notice] AH00169: caught SIGTERM, shutting down

These are normal operational messages rather than actual errors. The MPM (Multi-Processing Module) prefork messages indicate:

• Server startup completion (AH00163)
• Graceful shutdown initiation (AH00169)
• Process management events

The messages appear because:

1. Apache uses syslog-level notices for important operational events
2. MPM modules log their state transitions
3. Default logging configurations capture notices in error.log

To better manage these logs:

# In your apache configuration (httpd.conf or apache2.conf)
LogLevel warn
# Or specifically for MPM:
LogLevel mpm_prefork:warn

This will suppress notices while keeping important warnings. For detailed monitoring:

# Create separate log for MPM events
CustomLog /var/log/apache2/mpm.log "%t [%m:%l] %M"

The prefork MPM maintains a pool of child processes. Key parameters in your config:

<IfModule mpm_prefork_module>
    StartServers            5
    MinSpareServers         5
    MaxSpareServers        10
    MaxRequestWorkers      150
    MaxConnectionsPerChild  10000
</IfModule>

While these messages are normal, watch for patterns indicating problems:

• Frequent restarts (more than several per hour)
• Process count constantly at MaxRequestWorkers
• "Server reached MaxRequestWorkers" warnings

Create a simple monitoring script to track MPM events:

#!/bin/bash
# monitor_apache_mpm.sh
LOG_FILE="/var/log/apache2/error.log"
PATTERN="mpm_prefork:notice"

tail -F $LOG_FILE | grep --line-buffered $PATTERN | while read line
do
    echo "$(date) - MPM Event: $line" >> /var/log/apache2/mpm_monitor.log
    # Add notification logic here if needed
done

For production systems, consider using syslog-ng or rsyslog to properly categorize these messages:

# Example rsyslog configuration for Apache
if $programname == 'apache2' then {
    if $msg contains 'mpm_prefork:notice' then {
        /var/log/apache2/mpm_notices.log
        stop
    }
}

---

These log entries are completely normal operational messages from Apache's Multi-Processing Module (MPM) prefork implementation. Let's break down what each line means:

[Wed Jun 25 18:15:56.295408 2014] [mpm_prefork:notice] [pid 8817] AH00163: Apache/2.4.7 (Ubuntu) PHP/5.5.9-1ubuntu4 configured -- resuming normal operations
[Wed Jun 25 18:15:56.295570 2014] [core:notice] [pid 8817] AH00094: Command line: '/usr/sbin/apache2'
[Wed Jun 25 18:26:34.511247 2014] [mpm_prefork:notice] [pid 8817] AH00169: caught SIGTERM, shutting down

These specific messages typically appear during:

• Server startup (AH00163)
• Graceful shutdown (AH00169)
• Configuration reload

The prefork MPM creates multiple child processes that handle requests, with each process containing a single thread. This is different from worker or event MPMs that use multiple threads per process.

Key characteristics of prefork MPM:

• Process-based (not threaded)
• Each request handled by separate process
• Good for stability with non-thread-safe libraries

While these messages are normal, you might want to review your MPM prefork settings in apache2.conf or mpm_prefork.conf:

<IfModule mpm_prefork_module>
    StartServers             5
    MinSpareServers          5
    MaxSpareServers         10
    MaxRequestWorkers      150
    MaxConnectionsPerChild   0
</IfModule>

These messages only indicate problems if they appear:

• Too frequently (possible process recycling issues)
• Accompanied by error messages
• When server performance degrades

To check your current prefork status, you can use:

apachectl status
# Or for more detailed info:
apachectl fullstatus

For real-time monitoring, consider tools like:

• mod_status
• Apache's server-status handler
• Third-party monitoring solutions

Depending on your use case, you might consider:

# For threaded model (requires thread-safe PHP)
<IfModule mpm_worker_module>
    StartServers             2
    MinSpareThreads         25
    MaxSpareThreads         75
    ThreadLimit             64
    ThreadsPerChild         25
    MaxRequestWorkers      150
    MaxConnectionsPerChild   0
</IfModule>

# For event-based model (Apache 2.4+)
<IfModule mpm_event_module>
    StartServers             2
    MinSpareThreads         25
    MaxSpareThreads         75
    ThreadLimit             64
    ThreadsPerChild         25
    MaxRequestWorkers      150
    MaxConnectionsPerChild   0
</IfModule>

Remember to update your PHP configuration accordingly if switching MPM modules.