[ubuntu] suspend works, hibernate does not

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http://ubuntuforums.org – I have a ThinkPad X61 with Ubuntu 10.4 loaded. Everything runs fine except I now need to go long periods of time without power. The time is so long I need to change the battery. Unfortunately, I see the computer does not have the hibernate option, only suspend. Suspend mode requires a battery. I tried pm-hibernate. The screen just goes blank for a moment and then returns to normal. I tried loading the hibernate package. Still the same result. (Hardware)