How to create a swap for session usage

Context

Long silence from me past weeks as I was working on my home automation architecture, especially on IoT POV. I will publish everything here, but today I wanted to share a quick tip to create a swap space on a Linx system that doesn't have one.

Why so?

I'm deeply testing NanoPi NEO these days and without any doubt it will be my home automation corner stone. I started using the 256Mo version and the Ubuntu Core Linux image provided comes without any swap space.

As I started to make some composer update (because all my low level interaction is done with ReactPHP, stay tuned !), device exploded in such messages :

The following exception is caused by a lack of memory or swap, or not having swap configured
Check https://getcomposer.org/doc/articles/troubleshooting.md#proc-open-fork-failed-errors for details

PHP Warning:  proc_open(): fork failed - Cannot allocate memory in phar:///usr/local/bin/composer/vendor/symfony/console/Application.php on line 958

Warning: proc_open(): fork failed - Cannot allocate memory in phar:///usr/local/bin/composer/vendor/symfony/console/Application.php on line 958

  [ErrorException]                                   
  proc_open(): fork failed - Cannot allocate memory  

I forgot that 256Mo is not a lot... Solution : make a swap (that will stand until the next reboot)

# Use dd to create a 256 Mo sxap space, filled with 0, and named /var/swap.1
sudo /bin/dd if=/dev/zero of=/var/swap.1 bs=1M count=256

# Inform system that swap exists and where
sudo /sbin/mkswap /var/swap.1

# Enable
sudo /sbin/swapon /var/swap.1