Apache MPM Confusion -- Clarification Needed - apache

Question

I'm working on the linux box where i didn't compile and build Apache. I can't tell which Apache MPM (prefork or worker) I'm using because there seems to be executables for both in /usr/sbin/. This is a CentOS box:
httpd
httpd.worker
In the script /usr/sbin/apachectl is the following line:
# the path to your httpd binary, including options if necessary
HTTPD='/usr/sbin/httpd'
However, /usr/sbin/apachectl also shows HTTPD configuration in the following file which makes me believe it's overriding the above options for HTTPD and pointing it at httpd.worker:
$ cat /etc/sysconfig/httpd
# Configuration file for the httpd service.
#
# The default processing model (MPM) is the process-based
# 'prefork' model. A thread-based model, 'worker', is also
# available, but does not work with some modules (such as PHP).
# The service must be stopped before changing this variable.
#
HTTPD=/usr/sbin/httpd.worker
#
# To pass additional options (for instance, -D definitions) to the
# httpd binary at startup, set OPTIONS here.
#
#OPTIONS=
#
# By default, the httpd process is started in the C locale; to
# change the locale in which the server runs, the HTTPD_LANG
# variable can be set.
#
#HTTPD_LANG=C
#
# By default, the httpd process will create the file
# /var/run/httpd/httpd.pid in which it records its process
# identification number when it starts. If an alternate location is
# specified in httpd.conf (via the PidFile directive), the new
# location needs to be reported in the PIDFILE.
#
#PIDFILE=/var/run/httpd/httpd.pid
My conclusion is that i'm using MPM worker. However, why would i have an httpd executable in /usr/sbin that seems compiled as MPM prefork? Look at these commands? Artifacts maybe?:
# httpd -l
compiled in modules:
core.c
prefork.c
http_core.c
mod_so.c
$ httpd -V
Server version: Apache/2.2.15 (Unix)
Server built: Feb 13 2012 22:31:42
Server's Module Magic Number: 20051115:24
Server loaded: APR 1.3.9, APR-Util 1.3.9
Compiled using: APR 1.3.9, APR-Util 1.3.9
Architecture: 64-bit
Server MPM: Prefork
threaded: no
forked: yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/prefork"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=128
-D HTTPD_ROOT="/etc/httpd"
-D SUEXEC_BIN="/usr/sbin/suexec"
-D DEFAULT_PIDLOG="run/httpd.pid"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_LOCKFILE="logs/accept.lock"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="conf/mime.types"
-D SERVER_CONFIG_FILE="conf/httpd.conf"
$ httpd.worker -l
Compiled in modules:
core.c
worker.c
http_core.c
mod_so.c
$ apachectl -l
Compiled in modules:
core.c
worker.c
http_core.c
mod_so.c
# apachectl -V
Server version: Apache/2.2.15 (Unix)
Server built: Feb 13 2012 22:33:00
Server's Module Magic Number: 20051115:24
Server loaded: APR 1.3.9, APR-Util 1.3.9
Compiled using: APR 1.3.9, APR-Util 1.3.9
Architecture: 64-bit
Server MPM: Worker
threaded: yes (fixed thread count)
forked: yes (variable process count)
Server compiled with....
-D APACHE_MPM_DIR="server/mpm/worker"
-D APR_HAS_SENDFILE
-D APR_HAS_MMAP
-D APR_HAVE_IPV6 (IPv4-mapped addresses enabled)
-D APR_USE_SYSVSEM_SERIALIZE
-D APR_USE_PTHREAD_SERIALIZE
-D SINGLE_LISTEN_UNSERIALIZED_ACCEPT
-D APR_HAS_OTHER_CHILD
-D AP_HAVE_RELIABLE_PIPED_LOGS
-D DYNAMIC_MODULE_LIMIT=128
-D HTTPD_ROOT="/etc/httpd"
-D SUEXEC_BIN="/usr/sbin/suexec"
-D DEFAULT_SCOREBOARD="logs/apache_runtime_status"
-D DEFAULT_ERRORLOG="logs/error_log"
-D AP_TYPES_CONFIG_FILE="conf/mime.types"
-D SERVER_CONFIG_FILE="conf/httpd.conf"
the final reason I believe i'm running httpd.worker:
ps -C httpd.worker -F
UID PID PPID C SZ RSS PSR STIME TTY TIME CMD
root 13603 1 0 34690 4852 1 01:58 ? 00:00:00 /usr/sbin/httpd.worker
apache 13605 13603 0 34619 2352 1 01:58 ? 00:00:00 /usr/sbin/httpd.worker
apache 13606 13603 0 123554 7444 1 01:58 ? 00:00:00 /usr/sbin/httpd.worker
apache 13607 13603 0 240987 52604 0 01:58 ? 00:00:00 /usr/sbin/httpd.worker
apache 13609 13603 0 273755 52396 0 01:58 ? 00:00:00 /usr/sbin/httpd.worker
apache 13611 13603 0 290139 52128 0 01:58 ? 00:00:00 /usr/sbin/httpd.worker

Answer 1

If you are on CentOS, open /usr/sbin/apachectl and below the following lines you mentioned
# the path to your httpd binary, including options if necessary
HTTPD='/usr/sbin/httpd'
you will find the following lines:
# Source /etc/sysconfig/httpd for $HTTPD setting, etc.
if [ -r /etc/sysconfig/httpd ]; then
. /etc/sysconfig/httpd
fi
That is how your apachectl is grabbing and overriding apachectl own HTTPD variable.
This also means that you are indeed using worker mpm instead of prefork.