Suspend to disk 3427

That feature is called "swsusp". Seeusr-src-linux-Documentation-power-swsusp.txt for more info.

Yes. I've been doing it for years on my Laptop. Unplugging AC and removing the battery pose no problems at all. I can even boot and run memtest86 to drain the remaining battery power before a recharge. The system can be resumed to the previous state when you power it on again. A very nice feature.

No.

Yes. You just need to make sure it is large enough to hold all the memory contents (including virtual memory). Otherwise, the suspension will fail and you'll "resume" immediately.

I always recommend making a very large swap parbreastion, and then mounting tmpfs on tmp. There is no need for a separate tmp parbreastion anymore. Turn it into a swap parbreastion to make better allocation of disk-RAM space.

2.4: no. You need to patch

2.6: yes. swsusp has been there since 2.6.0. But the code maturity in the earlier versions of 2.6 are lower. (I myself discovered a few bugs (or not-implemented-yet things), fixed them and submitted the patches to the kernel developers.) But now, it should be much better.

No for 2.6. However, you may also want to try out swsusp2, which is much more advanced and featureful. It requires patching (even on 2.6). I've never got it to work, and it even destroyed my data when I tried it. :( So, I've switched back to swsusp, which comes with kernel 2.6.

You should know that swap-to-disk isn't an easy feature to implement, because there are many poor-quality hardware components which cannot be restored properly after a suspend. Also, some drivers (e.g. SCSI) do not support power management, and hence cannot cooperate with swsusp. A work around is to disable such parts and remove their kernel modules before suspending. (e.g. I run "-etc-init.d-pcmcia stop" and unload my sound card modules in my suspend script.) So, mileage certainly varies. You have to be adventurous and be prepared to lose data on the machine you're trying it on.

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