NAME

       systemd-sleep.conf, sleep.conf.d - Suspend and hibernation configuration file

SYNOPSIS

       /etc/systemd/sleep.conf

       /etc/systemd/sleep.conf.d/*.conf

       /run/systemd/sleep.conf.d/*.conf

       /usr/lib/systemd/sleep.conf.d/*.conf

DESCRIPTION

       systemd supports four general power-saving modes:

       suspend
           a low-power state where execution of the OS is paused, and complete power loss might
           result in lost data, and which is fast to enter and exit. This corresponds to suspend,
           standby, or freeze states as understood by the kernel.

       hibernate
           a low-power state where execution of the OS is paused, and complete power loss does
           not result in lost data, and which might be slow to enter and exit. This corresponds
           to the hibernation as understood by the kernel.

       hybrid-sleep
           a low-power state where execution of the OS is paused, which might be slow to enter,
           and on complete power loss does not result in lost data but might be slower to exit in
           that case. This mode is called suspend-to-both by the kernel.

       suspend-then-hibernate
           A low power state where the system is initially suspended (the state is stored in
           RAM). If the system supports low-battery alarms (ACPI _BTP), then the system will be
           woken up by the ACPI low-battery signal and hibernated (the state is then stored on
           disk). Also, if not interrupted within the timespan specified by HibernateDelaySec= or
           the estimated timespan until the system battery charge level goes down to 5%, then the
           system will be woken up by the RTC alarm and hibernated. The estimated timespan is
           calculated from the change of the battery capacity level after the time specified by
           SuspendEstimationSec= or when the system is woken up from the suspend.

       Settings in these files determine what strings will be written to /sys/power/disk and
       /sys/power/state by systemd-sleep(8) when systemd(1) attempts to suspend or hibernate the
       machine. See systemd.syntax(7) for a general description of the syntax.

CONFIGURATION DIRECTORIES AND PRECEDENCE

       The default configuration is set during compilation, so configuration is only needed when
       it is necessary to deviate from those defaults. Initially, the main configuration file in
       /etc/systemd/ contains commented out entries showing the defaults as a guide to the
       administrator. Local overrides can be created by editing this file or by creating
       drop-ins, as described below. Using drop-ins for local configuration is recommended over
       modifications to the main configuration file.

       In addition to the "main" configuration file, drop-in configuration snippets are read from
       /usr/lib/systemd/*.conf.d/, /usr/local/lib/systemd/*.conf.d/, and /etc/systemd/*.conf.d/.
       Those drop-ins have higher precedence and override the main configuration file. Files in
       the *.conf.d/ configuration subdirectories are sorted by their filename in lexicographic
       order, regardless of in which of the subdirectories they reside. When multiple files
       specify the same option, for options which accept just a single value, the entry in the
       file sorted last takes precedence, and for options which accept a list of values, entries
       are collected as they occur in the sorted files.

       When packages need to customize the configuration, they can install drop-ins under /usr/.
       Files in /etc/ are reserved for the local administrator, who may use this logic to
       override the configuration files installed by vendor packages. Drop-ins have to be used to
       override package drop-ins, since the main configuration file has lower precedence. It is
       recommended to prefix all filenames in those subdirectories with a two-digit number and a
       dash, to simplify the ordering of the files.

       To disable a configuration file supplied by the vendor, the recommended way is to place a
       symlink to /dev/null in the configuration directory in /etc/, with the same filename as
       the vendor configuration file.

OPTIONS

       The following options can be configured in the [Sleep] section of /etc/systemd/sleep.conf
       or a sleep.conf.d file:

       AllowSuspend=, AllowHibernation=, AllowSuspendThenHibernate=, AllowHybridSleep=
           By default any power-saving mode is advertised if possible (i.e. the kernel supports
           that mode, the necessary resources are available). Those switches can be used to
           disable specific modes.

           If AllowHibernation=no or AllowSuspend=no is used, this implies
           AllowSuspendThenHibernate=no and AllowHybridSleep=no, since those methods use both
           suspend and hibernation internally.  AllowSuspendThenHibernate=yes and
           AllowHybridSleep=yes can be used to override and enable those specific modes.

       SuspendMode=, HibernateMode=, HybridSleepMode=
           The string to be written to /sys/power/disk by, respectively, systemd-
           suspend.service(8), systemd-hibernate.service(8), or systemd-hybrid-sleep.service(8).
           More than one value can be specified by separating multiple values with whitespace.
           They will be tried in turn, until one is written without error. If none of the writes
           succeed, the operation will be aborted.

           The allowed set of values is determined by the kernel and is shown in the file itself
           (use cat /sys/power/disk to display). See the kernel documentation[1] for more
           details.

           systemd-suspend-then-hibernate.service(8) uses the value of SuspendMode= when
           suspending and the value of HibernateMode= when hibernating.

       SuspendState=, HibernateState=, HybridSleepState=
           The string to be written to /sys/power/state by, respectively, systemd-
           suspend.service(8), systemd-hibernate.service(8), or systemd-hybrid-sleep.service(8).
           More than one value can be specified by separating multiple values with whitespace.
           They will be tried in turn, until one is written without error. If none of the writes
           succeed, the operation will be aborted.

           The allowed set of values is determined by the kernel and is shown in the file itself
           (use cat /sys/power/state to display). See the kernel documentation[1] for more
           details.

           systemd-suspend-then-hibernate.service(8) uses the value of SuspendState= when
           suspending and the value of HibernateState= when hibernating.

       HibernateDelaySec=
           The amount of time the system spends in suspend mode before the system is
           automatically put into hibernate mode. Only used by systemd-suspend-then-
           hibernate.service(8). If the system has a battery, then defaults to the estimated
           timespan until the system battery charge level goes down to 5%. If the system has no
           battery, then defaults to 2h.

       SuspendEstimationSec=
           The RTC alarm will wake the system after the specified timespan to measure the system
           battery capacity level and estimate battery discharging rate, which is used for
           estimating timespan until the system battery charge level goes down to 5%. Only used
           by systemd-suspend-then-hibernate.service(8). Defaults to 1h.

EXAMPLE: FREEZE

       Example: to exploit the “freeze” mode added in Linux 3.9, one can use systemctl suspend
       with

           [Sleep]
           SuspendState=freeze

SEE ALSO

       systemd-sleep(8), systemd-suspend.service(8), systemd-hibernate.service(8), systemd-
       hybrid-sleep.service(8), systemd-suspend-then-hibernate.service(8), systemd(1),
       systemd.directives(7)

NOTES

        1. the kernel documentation
           https://www.kernel.org/doc/html/latest/admin-guide/pm/sleep-states.html#basic-sysfs-interfaces-for-system-suspend-and-hibernation