Composer killed while updating

The "Killed" message usually means your process consumed too much memory, so you may simply need to add more memory to your system if possible. At the time of writing this answer, I've had to increase my virtual machine's memory to at least 768MB in order to get composer update to work in some situations.

However, if you're doing this on a live server, you shouldn't be using composer update at all. What you should instead do is:

1. Run composer update in a local environment (such as directly on your physical laptop/desktop, or a docker container/VM running on your laptop/desktop) where memory limitations shouldn't be as severe.
2. Upload or git push the composer.lock file.
3. Run composer install on the live server.

composer install will then read from the .lock file, fetching the exact same versions every time rather than finding the latest versions of every package. This makes your app less likely to break, and composer uses less memory.

Read more here: https://getcomposer.org/doc/01-basic-usage.md#installing-with-composer-lock

Alternatively, you can upload the entire vendor directory to the server, bypassing the need to run composer install at all, but then you should run composer dump-autoload --optimize.

If like me, you are using some micro VM lacking of memory, creating a swap file does the trick:

#Check free memory beforefree -mmkdir -p /var/_swap_cd /var/_swap_#Here, 2G ~ 2GB of swap memory. Feel free to add MOREsudo fallocate -l 2G swapfilechmod 600 swapfilemkswap swapfileswapon swapfile#Automatically mount this swap partition at startupecho "/var/_swap_/swapfile none swap sw 0 0" >> /etc/fstab#Check free memory afterfree -m

As several comments pointed out, don't forget to add sudo if you don't work as root.

btw, feel free to select another location/filename/size for the file.
/var is probably not the best place, but I don't know which place would be, and rarely care since tiny servers are mostly used for testing purposes.

Unfortuantely composer requires a lot of RAM & processing power. Here are a few things that I did, which combined, made the process bearable. This was on my cloud playpen env.

1. You may be simply running out of RAM. Enable swap: https://www.digitalocean.com/community/search?q=add+swap (note: I think best practice is to add a seperate partition. Digitalocean's guide is appropriate for their environment)
2. service mysql stop (kill your DB/mem-hog services to free some RAM - don't forget to start it again!)
3. use a secondary terminal session running top to watch memory/swap consumption until process is complete.
4. composer.phar update --prefer-dist -vvv (verbose output [still hangs at some points when working] and use distro zip files). Maybe try a --dry-run too?
5. Composer is apparently know to run slower in older versions of PHP (e.g. 5.3x). It was still slow in 5.5.9 for me...