New Trick: Linux swapfile with systemd

_posts/2024-07-04-swapfile.md

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+---
+layout: post
+title:  "Linux swapfile with systemd"
+author: "rusty-snake"
+tags: swap swapfile systemd
+---
+
+**Preliminary notes:**
+
+ * This is a short transcript of the steps necessary to add a swapfile under linux. For a more detailed
+   explanation I refer to the [ArchWiki page](https://wiki.archlinux.org/title/Swap#Swap_file).
+ * Unlike the most other tutorials for swapfiles you will find in the internet that add the
+   swapfile to fstab, we will create a swapfile.swap systemd unit.
+ * This tutorial assumes that you have a working zram swap device with priority 100.
+
+## Create the swapfile
+
+~~~ bash
+mkswap --check -U clear --size 4G --file /swapfile
+~~~
+
+## Create a systemd swap unit for it
+
+~~~ bash
+systemctl edit --full --force swapfile.swap
+systemctl enable --now swapfile.swap
+~~~
+
+~~~ systemd
+[Unit]
+Description=Disk Swap on /swapfile
+
+[Swap]
+What=/swapfile
+Priority=50
+Options=discard
+
+[Install]
+WantedBy=swap.target
+~~~