systemd-hibernate-resume@.service, systemd-hibernate-resume — Resume from hibernation
systemd-hibernate-resume@.service
/usr/lib/systemd/systemd-hibernate-resume
systemd-hibernate-resume@.service
    initiates the resume from hibernation. It is instantiated with the
    device to resume from as the template argument.
systemd-hibernate-resume only supports
    the in-kernel hibernation implementation, known as
    swsusp.
    Internally, it works by writing the major:minor of specified
    device node to /sys/power/resume.
Failing to initiate a resume is not an error condition. It may mean that there was no resume image (e. g. if the system has been simply powered off and not hibernated). In such case, the boot is ordinarily continued.