Linux: What happens if you try to resume from suspend-to-disk when no...

salon_sue

My particular use case is that I have an encrypted root device which contains a swapfile (yes, I know that's slow, but it works well for my use case) and I'm embarking on an attempt to get suspend-to-disk working with a custom initramfs (as opposed to using the kernel parameters to accomplish this). The swapfile inside the encrypted root is the swap I intend for the hibernation image to be written to. (This is a good place to point out for...

Originally asked by AntiMS on Stack Exchange (unix) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

When the kernel performs hibernation it writes the special signature into the device header. When a resume is requested, the kernel checks for a valid signature and will refuse to resume from this device if the signature is not present. The signature is immediately cleared after the check and also if hibernation was not successful . As long as you ensure that a resume is attempted on every boot this protects against a stale image. You are correct that resume is synchronous. If execution reaches the code after echo N:M > /sys/power/resume it means that the resume attempt failed. Otherwise there is no verification that the hibernation image matches the currently booting system. It is also...

Full answer by Andrei Borzenkov: https://unix.stackexchange.com/a/806912 (CC BY-SA 4.0).

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