Composer proc_open(): fork failed - Cannot allocate memory -

i have same error others when running php ~/composer.phar update:

the following exception caused lack of memory , not having swap configured check https://getcomposer.org/doc/articles/troubleshooting.md#proc-open-fork-failed-errors details fatal error: uncaught exception 'errorexception' message 'proc_open(): fork failed - cannot allocate memory' in phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php:974 stack trace: 0 [internal function]: composer\util\errorhandler::handle(2, 'proc_open(): fo...', 'phar:///home/te...', 974, array) 1 phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php(974): proc_open('stty -a | grep ...', array, null, null, null, array) 2 phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php(784): symfony\component\console\application->getsttycolumns() 3 phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php(745): symfony\component\console\application->getterminaldimensions() 4 phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php(675): symfony\component\console\application->getterminalwidth() 5 phar:///home/tea/composer in phar:///home/tea/composer.phar/vendor/symfony/console/symfony/component/console/application.php on line 974 

...but large instance: 4gb ram , 4gb swap. free ram never exhausted, let alone available/cached ram, , swap isn't touched!

              total        used        free      shared  buff/cache   available mem:           3788         885        1908           9         993        2692 swap:          3967           0        3967 

it's first time running composer update on new machine, centos/cloudlinux 7.1 (with cpanel).

in desperation, i've tried # php -dmemory_limit=1g ../composer.phar update --no-scripts --prefer-dist , i've tried removing composer.lock , vendor files , tried adding temporary swap file but doesn't seem memory problem - error misguided?

proc_open not disabled , tried shell fork bomb protection disabled no jive.

would love heads up.

n.b. i'm aware of advice commit composer.lock file , composer install instance being used dev (as previous centos/cloudlinux 6.x machine smaller resource specs) need use same methods using previously.

i ran same problem. system had 1.5gb ram free , not enough...composer eating memory fast.

my solution clear cache , update latest version (1.4.2):

composer clear-cache  sudo composer selfupdate