Composer install/update not working

In first place You should try clearing composer cache.

rm -rf ~/.composer/cache

But more probably it's issue connected with available memory. Increasing memory_limit should help.

I had this issue and realised I had xdebug enabled. Disabling it fixed the issue for me.

Try with this one and make sure that the composer.json file exist in your project directory.

COMPOSER=composer.json composer update 

Try to view a verbose report:

composer install -vvv

or:

composer update -vvv

If last line shows that process is killed, you need to increase your swap memory:

sudo dd if=/dev/zero of=/swapfile bs=1024 count=512k
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile
swapon -s

if it continues killing the process, you need to increase 512k to 1024k or maybe 2048k