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Kubuntu 21.04 - how to get hibernate working when it appears disabled from kernel?

cn flag
eritbh

I'm using Kubuntu 21.04 and trying to hibernate/suspend-to-disk my laptop. I'm not having much luck. The errors I'm getting seem to suggest a deeper issue than all the other Q&As I've seen about this - most other answers seem to suggest echo disk | sudo tee /sys/power/state is the solution, but I can't even get that far. I've tried several things and ultimately ended up at the system sleep states documentation for the kernel, which says to check /sys/power/state and /sys/power/disk to see if it's even supported.

$ sudo systemctl hibernate
Failed to hibernate system via logind: Sleep verb "hibernate" not supported
$ echo disk | sudo tee /sys/power/state
disk
tee: /sys/power/state: Operation not permitted
$ cat /sys/power/state
freeze mem
$ cat /sys/power/disk
[disabled]

So it looks to me like my kernel doesn't support hibernation...? The sleep states docs also say,

Hibernation is supported if the CONFIG_HIBERNATION kernel configuration option is set. However, this option can only be set if support for the given CPU architecture includes the low-level code for system resume.

  • Is there a reason Kubuntu doesn't have it enabled by default but ships with a "Hibernate" action?
  • How would I go about enabling this option on the kernel?
  • This is pedantic, but is it important that my /sys/power/disk exists and reports [disabled] even though the kernel docs say it's supposed to not exist if hibernation is unsupported? Are the docs wrong?

Copypasta from system information:

Operating System: Kubuntu 21.04
KDE Plasma Version: 5.22.5
KDE Frameworks Version: 5.86.0
Qt Version: 5.15.2
Kernel Version: 5.11.0-38-generic (64-bit)
Graphics Platform: X11
Processors: 8 × 11th Gen Intel® Core™ i5-1135G7 @ 2.40GHz
Memory: 15.4 GiB of RAM
Graphics Processor: Mesa Intel® Xe Graphics

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cn flag
eritbh
@waltinator I have sufficient swap: 16 GB of RAM in my system, only a few GB of which is being used, and slightly more than 16 GB of swap. `pm-is-supported` does not exist as a command or man page on my system, and `man -k pm` lists nothing related (`man -k pm-`, which might be more specifically what you're trying to point me to?, lists nothing). Google has not helped me find where to install that tool - can you point to any package that includes it?
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cn flag
eritbh
I've found that `pm-is-supported` and friends come from the `pm-utils` apt package. `pm-is-supported --hibernate` gives a nonzero exit code, but doesn't give any additional information on why, and this doesn't tell me anything I didn't already know (hibernate is obviously not supported since `/sys/power/disk` reads `[disabled]`).
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waltinator avatar
it flag
waltinator
Hibernation requires enough `swap` space to save RAM. Look at `free`. Read `man free mkswap swapon pm-is-supported` (`pm` is Power Management, read `man -k pm`). Find the tools, use the tools.
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