How to Configure Hibernation on Ubuntu 24.04 with a Swap File
A practical walkthrough for enabling hibernation on Ubuntu 24.04 using a swap file instead of a partition, covering GRUB, initramfs pitfalls and the new polkit rules format.
This guide walks through enabling hibernation on Ubuntu 24.04 LTS using a swap.img file rather than a dedicated swap partition. It starts by locating the UUID of the partition hosting the swap file and its physical offset on disk, then adding these as resume and resume_offset parameters to GRUB_CMDLINE_LINUX_DEFAULT before running update-grub.
Two common pitfalls are specifically called out: creating a manual resume file under initramfs-tools, which triggers spurious warnings about a missing swap device, and using legacy init-premount scripts that try to manually write to /sys/power/resume during boot, causing a "sh: write error: invalid argument" failure. The recommended fix is to let the kernel read resume parameters directly from GRUB and avoid adding extra initramfs scripts.
The guide also highlights a change specific to Ubuntu 24.04: with polkit 122+, the older .pkla authorization format is silently ignored, and hibernation permissions must instead be granted via a JavaScript-based .rules file placed in /etc/polkit-1/rules.d. A seven-step debug checklist rounds out the guide, covering kernel command-line parameters, swap state, Secure Boot status, polkit authorization checks, and leftover initramfs scripts for cases where CanHibernate reports "no". This is a useful reference for sysadmins and desktop Linux users trying to understand why older hibernation tutorials no longer work on recent Ubuntu releases.