Hibernation
lastmod 2026-03-03created 2020-03-093 edits
Hibernation (Korean: choedae jeoljeon mode, 最大節電; also jaeugi) is a feature that writes all contents of system memory to non-volatile storage such as a hard disk before powering off the system. Many operating systems support this feature. When the computer is turned back on, the contents saved on the hard disk are loaded back into memory, returning the system to its original state, and the programs that were in use at the time continue to run as if nothing had happened. Entering hibernation and returning from it takes less time than restarting the system. Depending on the settings, hibernation can be made to run without invoking it manually.
To save the contents to the hard disk, the hard disk must have as much free space as the amount of memory installed in the system.
This feature is commonly used on laptop computers and runs automatically when the battery is low. Early hibernation features used the BIOS, but in modern systems the operating system manages it directly. This feature is defined as sleeping mode S4 in the ACPI specification.
This feature is called hibernation in English; in Korean, the Microsoft Windows operating system renders it as choedae jeoljeon mode ("maximum power-saving mode"), and Mac OS renders it as jaeugi ("putting to sleep").
Making it work even when the laptop lid (LID) is closed
See Systemd#Adjusting laptop screen-off behavior.