pcntl no funciona en Ubuntu 'por razones de seguridad'

Instalé pcntl en mi PHP 5.4.6 ejecutándose en Ubuntu 12.10 de 32 bits, usando este artículo.

No salió nada bien porque después de compilar, al ejecutarlo make testobtuve los siguientes errores. Recibo una advertencia cada vez que intento bifurcar un proceso secundario que dice:

Advertencia: pcntl_fork() se ha deshabilitado por razones de seguridad en /var/www/mydev/dev/mailServiceTest.php en la línea 8

Busqué una solución en toda la web, pero desafortunadamente no encontré ninguna mención de este problema en ningún otro lugar.

    Build complete.
Don't forget to run 'make test'.
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0

=====================================================================
PHP         : /usr/bin/php 
Warning: Module 'pcntl' already loaded in Unknown on line 0

PHP_SAPI    : cli
PHP_VERSION : 5.4.6-1ubuntu1.2
ZEND_VERSION: 2.4.0
PHP_OS      : Linux - Linux oleg-Lenovo-G580 3.5.0-26-generic #42-Ubuntu SMP Fri Mar 8 23:20:06 UTC 2013 i686
INI actual  : /php/php-5.4.6/ext/pcntl/tmp-php.ini
More .INIs  :  
CWD         : /php/php-5.4.6/ext/pcntl
Extra dirs  : 
VALGRIND    : Not used
=====================================================================
TIME START 2013-04-28 12:11:03
=====================================================================
FAIL Test pcntl wait functionality [tests/001.phpt] 
FAIL pcntl: pcntl_sigprocmask(), pcntl_sigwaitinfo(), pcntl_sigtimedwait() [tests/002.phpt] 
FAIL pcntl: SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK [tests/003.phpt] 
FAIL Bug #47566 (return value of pcntl_wexitstatus()) [tests/bug47566.phpt] 
FAIL pcntl_alarm() [tests/pcntl_alarm.phpt] 
FAIL pcntl_exec() [tests/pcntl_exec.phpt] 
FAIL pcntl_exec() 2 [tests/pcntl_exec_2.phpt] 
FAIL pcntl_exec() 3 [tests/pcntl_exec_3.phpt] 
FAIL Test function pcntl_fork() by calling it with its expected arguments [tests/pcntl_fork_basic.phpt] 
FAIL Test function pcntl_fork() by testing the process isolation in the forking hierarchy father -> son -> grandson where father can not knows his grandson [tests/pcntl_fork_variation.phpt] 
FAIL Test pcntl_get_last_error() [tests/pcntl_get_last_error.phpt] 
FAIL pcntl_signal() [tests/pcntl_signal.phpt] 
FAIL pcnt_signal_dispatch() [tests/pcntl_signal_dispatch.phpt] 
FAIL pcntl_wait() [tests/pcntl_wait.phpt] 
FAIL Closures as a signal handler [tests/signal_closure_handler.phpt] 
=====================================================================
TIME END 2013-04-28 12:11:07

=====================================================================
TEST RESULT SUMMARY
---------------------------------------------------------------------
Exts skipped    :    0
Exts tested     :   44
---------------------------------------------------------------------

Number of tests :   15                15
Tests skipped   :    0 (  0.0%) --------
Tests warned    :    0 (  0.0%) (  0.0%)
Tests failed    :   15 (100.0%) (100.0%)
Expected fail   :    0 (  0.0%) (  0.0%)
Tests passed    :    0 (  0.0%) (  0.0%)
---------------------------------------------------------------------
Time taken      :    4 seconds
=====================================================================

=====================================================================
FAILED TEST SUMMARY
---------------------------------------------------------------------
Test pcntl wait functionality [tests/001.phpt]
pcntl: pcntl_sigprocmask(), pcntl_sigwaitinfo(), pcntl_sigtimedwait() [tests/002.phpt]
pcntl: SIG_BLOCK, SIG_UNBLOCK, SIG_SETMASK [tests/003.phpt]
Bug #47566 (return value of pcntl_wexitstatus()) [tests/bug47566.phpt]
pcntl_alarm() [tests/pcntl_alarm.phpt]
pcntl_exec() [tests/pcntl_exec.phpt]
pcntl_exec() 2 [tests/pcntl_exec_2.phpt]
pcntl_exec() 3 [tests/pcntl_exec_3.phpt]
Test function pcntl_fork() by calling it with its expected arguments [tests/pcntl_fork_basic.phpt]
Test function pcntl_fork() by testing the process isolation in the forking hierarchy father -> son -> grandson where father can not knows his grandson [tests/pcntl_fork_variation.phpt]
Test pcntl_get_last_error() [tests/pcntl_get_last_error.phpt]
pcntl_signal() [tests/pcntl_signal.phpt]
pcnt_signal_dispatch() [tests/pcntl_signal_dispatch.phpt]
pcntl_wait() [tests/pcntl_wait.phpt]
Closures as a signal handler [tests/signal_closure_handler.phpt]
=====================================================================

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oleg@oleg-Lenovo-G580:/php/php-5.4.6/ext/pcntl$ version

Al escribir el siguiente comando, parece que PHP ya está instalado, aunque el intérprete de PHP no reconoció la función antes de instalar esta extensión:

oleg@oleg-Lenovo-G580:/php/php-5.4.6/ext/pcntl$ php -m | grep pcntl
PHP Warning:  Module 'pcntl' already loaded in Unknown on line 0
pcntl

¿Cómo puedo configurar esta característica para que funcione correctamente?

Jan 01 '70 08:01 Oleg Belousov