rtcwake

Schedule system wake from sleep using RTC alarm

TLDR

Show alarm status

$ sudo rtcwake -m show -v

Suspend to RAM and wake after 10 seconds

$ sudo rtcwake -m mem -s 10

Suspend to disk and wake in 15 minutes

$ sudo rtcwake -m disk --date +15min

Freeze and wake at specific time

$ sudo rtcwake -m freeze --date [YYYYMMDDhhmm]

Disable alarm

$ sudo rtcwake -m disable

Dry run without actually suspending

$ sudo rtcwake -m mem -s 600 -n

List supported wake modes for this kernel

$ rtcwake --list-modes

SYNOPSIS

rtcwake [options] [-d device] [-m mode] {-s seconds | -t timet | **--date** timestamp_}

rtcwake enters a system sleep state and configures the RTC (Real-Time Clock) to wake the system at a specified time. It's useful for scheduled tasks, power saving, and automatic system wake.The tool supports various sleep modes with different power/wake trade-offs. The RTC alarm persists even if the system loses power (battery backup).

PARAMETERS

-m, --mode mode

Sleep / action mode (see MODES).

-s, --seconds sec

Wake sec seconds from now.

-t, --time timet_

Wake at the absolute Unix epoch time timet_.

--date timestamp

Wake at the given timestamp (e.g. `+5min`, `2026-04-30 18:00`, `tomorrow 03:00`).

-d, --device rtc

Use the specified RTC device (default /dev/rtc0).

-l, --local

Treat the hardware clock as local time.

-u, --utc

Treat the hardware clock as UTC.

-a, --auto

Read the clock interpretation from /etc/adjtime (default).

-A, --adjfile file

Use file instead of /etc/adjtime.

-n, --dry-run

Test mode — set up the alarm but do not actually suspend or shut down.

--list-modes

Print modes the running kernel supports.

-v, --verbose

Verbose output.

-V, --version

Print version and exit.

MODES

standby

ACPI S1 — minimal but real power savings. Default mode if -m is omitted.

mem

Suspend to RAM (ACPI S3).

disk

Suspend to disk / hibernate (ACPI S4).

freeze

Suspend-to-idle (S0ix), kernel 3.9+.

off

Power off the system (ACPI S5).

Set the RTC alarm but do not suspend or shut down.

Do not sleep; instead poll the RTC until the alarm fires (debugging).

show

Display the currently set alarm.

disable

Cancel a pending alarm.

CAVEATS

Requires root privileges. Not all hardware supports all modes. Time is relative to hardware clock (usually UTC). BIOS/UEFI must support RTC wake.

HISTORY

rtcwake is part of util-linux, providing a standard interface to the Linux RTC wake functionality used for scheduled wake-ups and automated power management.