linux 定时休眠的实现思路

# SPDX-License-Identifier: LGPL-2.1+
## This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Suspend
Documentation=man:systemd-suspend.service(8)
DefaultDependencies=no
Requires=sleep.target
After=sleep.target
[Service]
Type=oneshot
ExecStart=/usr/lib/systemd/systemd-sleep suspend

sudo dd if=/dev/zero of=/swapfile bs=10240 count=524288
sudo mkswap /swapfile
sudo chmod 0600 /swapfile
sudo swapon /swapfile
sudo cp /etc/fstab /etc/fstab.bak
echo "/swapfile swap swap default 0 0" |tee -a /etc/fstab
Setting up swapspace version 1, size = 5 GiB (5368705024 bytes)
no label, UUID=d0f0c682-e1fa-416f-8fe2-b554b8ca363a
/swapfile swap swap default 0 0

NAME  TYPE  SIZE USED PRIO
/dev/sda2 partition 8G 280K -2
/swapfile file  5G 0B -3

sudo sed -i '/GRUB_CMDLINE_LINUX_DEFAULT/ s!"$! resume=/dev/sda2"!' /etc/default/grub

sudo filefrag -v /swapfile|head -5
Filesystem type is: ef53
File size of /swapfile is 5368709120 (1310720 blocks of 4096 bytes)
 ext:  logical_offset:  physical_offset: length: expected: flags:
 0:  0.. 32767: 4653056.. 4685823: 32768:   
 1: 32768.. 65535: 4685824.. 4718591: 32768:

sudo sed -i '/GRUB_CMDLINE_LINUX_DEFAULT/ s!"$! resume=/dev/sda3 resume_offset=4653056"!' /etc/default/grub

sudo sed -i '/^HOOKS=/ s/)/ resume)/' /etc/mkinitcpio.conf

sudo mkinitcpio -g /boot/initramfs-linux-lily.img
==> Starting build: 4.16.12-2-lily
 -> Running build hook: [base]
 -> Running build hook: [udev]
 -> Running build hook: [autodetect]
 -> Running build hook: [modconf]
 -> Running build hook: [block]
 -> Running build hook: [filesystems]
 -> Running build hook: [keyboard]
 -> Running build hook: [fsck]
 -> Running build hook: [resume]
==> Generating module dependencies
==> Creating gzip-compressed initcpio image: /boot/initramfs-linux-lily.img
==> Image generation successful

# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Hibernate
Documentation=man:systemd-suspend.service(8)
DefaultDependencies=no
Requires=sleep.target
After=sleep.target
[Service]
Type=oneshot
ExecStart=/usr/lib/systemd/systemd-sleep hibernate

# SPDX-License-Identifier: LGPL-2.1+
#
# This file is part of systemd.
#
# systemd is free software; you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation; either version 2.1 of the License, or
# (at your option) any later version.
[Unit]
Description=Hybrid Suspend+Hibernate
Documentation=man:systemd-suspend.service(8)
DefaultDependencies=no
Requires=sleep.target
After=sleep.target
[Service]
Type=oneshot
ExecStart=/usr/lib/systemd/systemd-sleep hybrid-sleep

SYSTEMD-SUSPEND.SERVICE(8) systemd-suspend.service SYSTEMD-SUSPEND.SERVICE(8)
NAME
  systemd-suspend.service, systemd-hibernate.service, systemd-hybrid-
  sleep.service, systemd-sleep - System sleep state logic
SYNOPSIS
  systemd-suspend.service
  systemd-hibernate.service
  systemd-hybrid-sleep.service
  /usr/lib/systemd/system-sleep
DESCRIPTION
  systemd-suspend.service is a system service that is pulled in by
  suspend.target and is responsible for the actual system suspend.
  Similarly, systemd-hibernate.service is pulled in by hibernate.target
  to execute the actual hibernation. Finally,
  systemd-hybrid-sleep.service is pulled in by hybrid-sleep.target to
  execute hybrid hibernation with system suspend.
  Immediately before entering system suspend and/or hibernation
  systemd-suspend.service (and the other mentioned units, respectively)
  will run all executables in /usr/lib/systemd/system-sleep/ and pass two
  arguments to them. The first argument will be "pre", the second either
  "suspend", "hibernate", or "hybrid-sleep" depending on the chosen
  action. Immediately after leaving system suspend and/or hibernation the
  same executables are run, but the first argument is now "post". All
  executables in this directory are executed in parallel, and execution
  of the action is not continued until all executables have finished.
  Note that scripts or binaries dropped in /usr/lib/systemd/system-sleep/
  are intended for local use only and should be considered hacks. If
  applications want to react to system suspend/hibernation and resume,
  they should rather use the Inhibitor interface[1].
  Note that systemd-suspend.service, systemd-hibernate.service, and
  systemd-hybrid-sleep.service should never be executed directly.
  Instead, trigger system sleep states with a command such as "systemctl
  suspend" or similar.
  Internally, this service will echo a string like "mem" into
  /sys/power/state, to trigger the actual system suspend. What exactly is
  written where can be configured in the "[Sleep]" section of
  /etc/systemd/sleep.conf or a sleep.conf.d file. See systemd-
  sleep.conf(5).
OPTIONS
  systemd-sleep understands the following commands:
  -h, --help
   Print a short help text and exit.
  --version
   Print a short version string and exit.
  suspend, hibernate, hybrid-sleep
   Suspend, hibernate, or put the system to hybrid sleep.
SEE ALSO
  systemd-sleep.conf(5), systemd(1), systemctl(1), systemd.special(7),
  systemd-halt.service(8)
NOTES
  1. Inhibitor interface

[Unit]
Description=Hibernate every 21:30:00
[Timer]
OnCalendar=*-*-* 21:30:00
Persistent=true
Unit=systemd-hibernate.service
[Install]
WantedBy=timers.target

sudo rtcwake -m ${mode} -t ${time_t}
# 或者
sudo rtcwake -m ${mode} -s ${seconds}