Memory on a 2 GB VPS

Read the right column

In the output of free -m the free column is almost always small, and that is fine: the kernel uses spare memory for the page cache. The number that matters is available, an estimate of how much can be handed to programs without swapping.

Who is using it

ps -eo rss,comm --sort=-rss | head

If something was killed for lack of memory, the kernel says so:

journalctl -k | grep -i 'out of memory'

A small swap file

Swap will not make a small machine fast, but it gives the kernel somewhere to put memory that was touched once at startup and never again:

fallocate -l 1G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
echo '/swapfile none swap sw 0 0' >> /etc/fstab

Swappiness

The default of 60 lets the kernel swap out idle programs rather eagerly. On a server where the working set fits in RAM, a lower value keeps them resident:

echo 'vm.swappiness=10' > /etc/sysctl.d/60-swappiness.conf
sysctl --system