systemctl-hibernate

Hibernate the system immediately

$ systemctl hibernate

$ systemctl hibernate --force

$ systemctl hibernate --no-wall

systemctl [OPTIONS...] hibernate

--no-block
    Do not wait for the operation to finish. The command will return immediately after queuing the hibernation request, allowing other tasks to continue in the foreground.

--dry-run
    Show what would be done without actually performing the hibernation operation. This is useful for testing configurations or understanding the execution path without altering the system state.

systemctl hibernate is a command used on Linux systems utilizing systemd to initiate the system's hibernation process. Hibernation, also known as Suspend-to-Disk, saves the entire current state of the computer's random access memory (RAM) to a dedicated swap partition or swap file on the hard drive before powering down the machine completely. When the system is powered back on, the contents of the RAM are reloaded from the disk, allowing the user to resume their work exactly where they left off, with all applications and open documents restored. This differs from a regular shutdown, which closes all programs, and from suspension (Suspend-to-RAM), which keeps the RAM powered and consumes minimal energy. Hibernation is useful for saving power over long periods without closing open work, but it requires sufficient disk space (typically equal to or greater than the amount of installed RAM) for the swap area.

Swap Space Requirement:
For hibernation to function correctly, your system must have a swap partition or a swap file at least as large as the amount of installed RAM. Insufficient swap space will prevent successful hibernation.

Kernel Configuration:
In some cases, the kernel might need to be explicitly told where to find the swap space for resuming. This is typically done via the resume=/dev/SWAP_DEVICE or resume_offset=OFFSET kernel parameter in your bootloader configuration (e.g., GRUB).

Hardware and Driver Compatibility:
Not all hardware or proprietary drivers (especially for graphics cards) fully support hibernation, which can lead to issues such as a black screen, system freeze, or inability to resume. Updating drivers or kernel might resolve these.

Dual-Boot Systems and Fast Startup:
If you dual-boot with Windows, ensure that Windows 'Fast Startup' feature is disabled. If enabled, Windows might not fully release its hold on the filesystem, leading to potential data corruption if Linux attempts to hibernate and resume from a shared NTFS partition.

Resume Time:
Resuming from hibernation can take significantly longer than resuming from suspend (Suspend-to-RAM) due to the need to read the entire RAM contents from disk.

When systemctl hibernate is executed, the kernel first copies the entire contents of the system's RAM into a pre-configured swap area (either a partition or a file). Once this operation is complete, the system powers down completely, consuming no power. Upon restart, the bootloader and kernel detect the presence of the hibernation image in the swap area and load it back into RAM, restoring the system to its exact state prior to hibernation. This process ensures that all running applications, open files, and user sessions are preserved.

If hibernation fails to work or resume properly, consider the following:
Verify Swap Size: Ensure your swap space is equal to or greater than your RAM.
Kernel Parameters: Confirm that your bootloader (e.g., GRUB) is correctly configured with the resume= parameter pointing to your swap device.
Check Logs: Review system logs (journalctl -b -1 for the previous boot) for hibernation-related errors.
Driver Issues: Update proprietary drivers, especially for graphics, as they can sometimes interfere with power management states.
Disable Fast Startup (Windows): If dual-booting, ensure Windows 'Fast Startup' is disabled.

The concept of system hibernation has existed in Linux for many years, initially managed by tools like pm-utils and direct kernel interfaces. With the widespread adoption of systemd as the init system in major Linux distributions (such as Fedora, Debian, Ubuntu, and Arch Linux), power management functions, including hibernation, were integrated into the systemctl command-line utility. This provided a unified and standardized way to control system states. The systemctl hibernate command replaced older, less consistent methods, offering a more robust and predictable mechanism for suspending the system to disk, leveraging systemd's comprehensive system management capabilities. Its development aligns with systemd's goal of centralizing and streamlining various system administration tasks.

systemctl(1), systemctl suspend(1), systemctl poweroff(1), systemctl reboot(1), systemctl suspend-then-hibernate(1), systemd(1), swap(8)