Old Raspberry Pi models

While these Raspberry Pi models may sometimes be able to ostensibly run the Minecraft server, they don't have enough memory to really support one. Your mileage with running a server may vary, and it might run quite slow.

You can run the server off a swap file. This is basically pretending a part of your SD-card is RAM, and using it as such. RAM is good for a lot of random I/O reads and writes, however, flash cards and Raspberry Pis in general are not great at this. As a result, this will probably be quite slow, and if you want to use this, I recommend having an A1 or A2 rated microSD card as bootdisk.

I would recommend you keep memory allocation at a minimum (512MB for 1-5 players, 1GB for anything above) in order to force the Minecraft server to flush memory often and be conservative with memory activity. You can find lots of guides on the internet for how to increase the swapfile, and here is an example of how you would create a 512MB swapfile.

1. Disable the active swapfile.
2. Edit the swapfile configuration. Change the line beginning with CONF_SWAPSIZE to CONF_SWAPSIZE=512.
3. Initialize the new swapfile configuration and re-enable the swapfile.
4. Reboot.

sudo dphys-swapfile swapoff
sudo nano /etc/dphys-swapfile
sudo dphys-swapfile setup && sudo dphys-swapfile swapon
sudo reboot

That should be it. You should now be able to run the run.sh file without running into any issues.