The first step is to determine which MPM (Multi-Processing Module) your Apache installation is actually using. On Debian systems, you can check this with:

apache2ctl -V | grep -i mpm

If you're not seeing any MPM modules in mods-available or mods-enabled, it's likely you're using the default prefork module, which is common for older systems and PHP applications.

With only 448MB RAM, we need to be extremely conservative. A good rule of thumb is to allocate:

• ~100MB for OS overhead
• ~50MB for other services
• Leaving ~300MB for Apache

Each Apache process in prefork typically uses 10-20MB. So we should aim for no more than 15-20 total processes.

For your mpm_prefork_module, try these settings:

    StartServers         2
    MinSpareServers      2
    MaxSpareServers      5
    MaxClients          15
    MaxRequestsPerChild 1000

• StartServers 2: Begin with just 2 processes to conserve memory
• MinSpareServers 2: Keep minimum spare processes low
• MaxSpareServers 5: Prevent too many idle processes
• MaxClients 15: Hard limit to stay within memory constraints
• MaxRequestsPerChild 1000: Recycle processes periodically to prevent memory leaks

Consider adding these to your configuration:

# Reduce keepalive settings
KeepAlive Off
# Or if you must have it:
KeepAlive On
KeepAliveTimeout 2
MaxKeepAliveRequests 50

# Disable unneeded modules
# Example:
# a2dismod auth_basic authn_file authz_default authz_groupfile authz_user autoindex

Install and configure apachetop to monitor in real-time:

sudo apt-get install apachetop
apachetop -f /var/log/apache2/access.log

For process-level monitoring:

watch -n 5 "ps -ylC apache2 --sort:rss | head -20"

If you're still having memory issues:

• Switch to lighttpd or nginx which are lighter
• Implement a cron job to gracefully restart Apache nightly
• Upgrade to a more modern lightweight distro like Alpine Linux

The first critical step is determining which Multi-Processing Module (MPM) your Apache instance is actually using. On Debian systems, run:

apache2 -V | grep -i mpm
# Example output:
# Server MPM:     prefork

With only 448MB RAM available (shared with OS and other services), we need aggressive optimization:

# Formula for MaxClients in prefork:
MaxClients ≈ (Total RAM - (OS + other services)) / Average Apache process size

# For a typical 30MB Apache process:
(448 - 100) / 30 = ~11 MaxClients

    StartServers          2
    MinSpareServers       2
    MaxSpareServers       4
    MaxClients           10
    MaxRequestsPerChild 1000

    StartServers          1
    MinSpareThreads      10
    MaxSpareThreads      20
    ThreadLimit          20
    ThreadsPerChild      10
    MaxClients           20
    MaxRequestsPerChild 1000

• Enable KeepAlive with short timeout: KeepAliveTimeout 2
• Reduce timeout: Timeout 30
• Disable unused modules: a2dismod autoindex status

# Check memory usage:
ps -ylC apache2 --sort:rss | head -10

# Real-time monitoring:
watch -n 1 "free -m && echo '' && ps -eo pid,user,comm,pmem --sort -pmem | head -5"