Create a swapfile for your Linux server

[Discourse]

For servers with <= 4GB of RAM, running ./discourse-setup will prompt for and automatically create a 2GB swapfile.

Most cloud virtual machine providers do not set up swapfiles as part of their server provisioning.

In particular, upgrading Discourse produces a lot of memory pressure. With a swap file, rather than randomly terminating processes with an out of memory error, things will slow down instead. Having a swap file is a cheap insurance policy that protects you from many other load related failures.

This can be done at any time from the command line on your server.

Set up a 2GB swap file

We recommend a 2GB swap file for Discourse, unless your server has more than 4GB of memory.

In the shell you have opened to your droplet, do the following:

You will need to be root for much of this, so either be root or sudo -s before running these commands! Don’t forget to exit root afterwards.

1. Create an empty swapfile

    install -o root -g root -m 0600 /dev/null /swapfile
   

2. Allocate a 2GB file named ‘swapfile’

    fallocate -l 2G /swapfile
   

3. tell linux this is the swap file:

    mkswap /swapfile
   

4. Activate it

    swapon /swapfile
   

5. Add it to the file system table so its there after reboot:

    echo "/swapfile       swap    swap    auto      0       0" | tee -a /etc/fstab
   

6. Set the swappiness to 10 so its only uses as an emergency buffer

    sysctl -w vm.swappiness=10
    echo 'vm.swappiness = 10' > /etc/sysctl.d/30-discourse-swap.conf
   

The whole thing as a single copy and pastable script:

install -o root -g root -m 0600 /dev/null /swapfile
fallocate -l 2G /swapfile
mkswap /swapfile
swapon /swapfile
echo "/swapfile       swap    swap    auto      0       0" | tee -a /etc/fstab
sysctl -w vm.swappiness=10
echo 'vm.swappiness = 10' > /etc/sysctl.d/30-discourse-swap.conf

Last edited by @JammyDodger 2022-05-23T18:45:59Z

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