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I can hibernate my laptop via pm-hibernate command without any problems. I want to achieve the same results manually. For this to work,

  1. I need to take a snapshot and dump the contents of RAM+swap into a file (or /dev/myswap2), like:

    dd if=/dev/fmem of=path/to/memory.img

  2. Resume from that file on the next boot, possibly by setting resume=path/to/memory.img option within GRUB.

How can I take a snapshot of RAM and Swap in order to dump them into a file (or block device) for hibernation purposes?

Intention

I can

  • take a snapshot of my whole filesystem while the system is running
  • send the snapshots to a target disk
  • replace necessary files (like /etc/fstab, /etc/crypttab, /boot/grub/grub.cfg etc.) to make the target bootable

So, when I unplug my USB disk, it's ready to boot my (or similar) computer, which cuts the MTTR down to ~10 minutes in case of a disk failure. (~1 minute to boot and ~9 minutes to reopen my applications, rearrange the windows, etc. after login.)

My intention is that if I could take a snapshot of my RAM in the same way the pm-hibernate does and write it to the target disk's swap area, then I could boot into the exact same state of backup moment (as if my target disk is hibernated) in such a disk failure scenario.

ceremcem
  • 2,351

1 Answers1

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You can transition by writing into /sys/power/state one of sleep states contained inside, es.

echo disk > /sys/power/state

Available states are:

  • freeze (Suspend-to-Idle)
  • standby (Power-On Suspend)
  • mem (Suspend-to-RAM)
  • disk (Suspend-to-Disk)

/sys/power/disk controls the operating mode of hibernation (Suspend-to-Disk).

Available options are:

  • `platform' (put the system into sleep using a platform-provided method)
  • shutdown (shut the system down)
  • reboot (reboot the system)
  • suspend (trigger a Suspend-to-RAM transition)
  • test_resume (resume-after-hibernation test mode)

References

Linux kernel documentation

Scrooge McDuck
  • 1,084
  • Writing to /sys/power/state will trigger an actual hibernate, is that correct? If so, I don't want to hibernate my computer during a backup operation, I only want to "simulate" it. – ceremcem Jan 05 '21 at 14:07
  • Try check ACPI code. From the reference: "the 'platform' option is only available if the platform provides a special mechanism to put the system to sleep after creating a hibernation image (ACPI does that, for example)." – Scrooge McDuck Jan 05 '21 at 15:18