Using Windows pagefile as Encrypted Swap

Ask Fedora
1

Hello there!

I have migrated back to linux a couple of days ago but I intend to keep my windows 10 system for a while. My laptop has a small SSD drive, which is ideal for swap in my opinion. Problem is: I just have a few gigabytes available. I have, though, a huge pagefile.sys that windows uses for swap.

I don’t wanna waste 16 precious gigabytes by having a different swap for each system. I don’t plan to hybernate my W10 any longer, so that won’t be a problem. So I have formatted this file as swap with mkswap and activated with swapon.

Problem is: I would like this swap to be encrypted.

Any instructions on how to do that? I need some guidance for:

  • Encrypting it and mapping it
  • Understanding how cryptsetup would manage that, as W10, if booted, might overwrite the pagefile, therefore something possibly important for cryptsetup to work (??? I guess, I’m unsure)
  • I don’t mind activating it manually as needed, if I need to setup encryption again after booting W10, but if I could to this automatically that would be perfect.

Sincerely,
Daph

2

Windows WILL overwrite anything in the pagefile.sys file. Windows also creates and uses that file dynamically so it may change at times for you.

IMHO this is a very bad idea if you intend to continue to dual boot.

With fedora 33, 34, and now 35 a swap file/partition is not necessary unless you intend to hibernate fedora since by default fedora creates a virtual swap space using zram which can be seen using zramctl. Having a physical swap as well can in many instances be counterproductive.

I would recommend you NOT use a physical swap space since zram is in memory and thus is volatile. A simple power off will eliminate everything there (although suspend keeps it in memory and hibernate writes to a physical swap space)

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3

Hello,

First of all, thank you for your reply.

I like the whole zram idea. However, I indeed intend to hibernate, that’s why I decided to setup a swap in the first place (that’s also why I’m worried about encryption).

And indeed, I think you’re right about the pagefile.sys idea, I better make some room for another file (as room for another partition would be really difficult). Anyway, I still don’t know how to do that and would appreciate any ideas.

Thanks!

– Daph

4

You could check if this How-To still works.

https://discussion.fedoraproject.org/t/howto-hibernate-into-swap-file/73020

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