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I am using Ubuntu 10.04 System. In that, I am trying to wake-up my system automatically at specific time.For that,I wrote a python script for wake-up automatically.The script was run perfectly and I was checked in this location /sys/class/rtc/rtc0/wakealaram.The wake-up time was successfully wrote in this wakealaram file. But the system is not waked-up at specified time. If you have any idea about this problem, let me.It is very useful to me.

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Could you share your python script. Are you using rtcwake? – Khurshid Alam Mar 25 '13 at 9:07
os.system('echo %(passwd)s | sudo -S sh -c "echo 0 > /sys/class/rtc/rtc0/wakealarm"' % locals()) os.system('echo %(passwd)s | sudo -S sh -c "echo %(alarmtime)s > /sys/class/rtc/rtc0/wakealarm"' % locals()) – Viswa Mar 25 '13 at 9:16
Modifying /sys/class/rtc/rtc0/wakealarm is not the right thing to do. There is inbuilt command for this: `rtcwake'. You should try with that. – Khurshid Alam Mar 27 '13 at 9:19


The command that you are interested in is rtcwake:

This program is used to enter a system sleep state until specified wakeup time.


To find the correct syntax that works for you try the following:

sudo rtcwake -u -s 60 -m mem

This should suspend the computer for 60 seconds before restoring. The significant parameter is mem You have several options you can choose - play to find the value that works best for you:

                 ACPI state S1. This state offers  minimal,  though  real,
                 power savings, while providing a very low-latency transi‐
                 tion back to a working system. This is the default mode.

          mem    ACPI state S3 (Suspend-to-RAM). This state offers signif‐
                 icant  power  savings  as everything in the system is put
                 into a low-power  state,  except  for  memory,  which  is
                 placed in self-refresh mode to retain its contents.

          disk   ACPI  state  S4  (Suspend-to-disk). This state offers the
                 greatest power savings, and  can  be  used  even  in  the
                 absence  of  low-level platform support for power manage‐
                 ment. This state operates  similarly  to  Suspend-to-RAM,
                 but  includes  a final step of writing memory contents to

          off    ACPI  state  S5  (Poweroff).  This  is  done  by  calling
                 '/sbin/shutdown'.   Not officially supported by ACPI, but
                 usually working.

          no     Don't suspend. The rtcwake command sets RTC  wakeup  time

          on     Don't  suspend,  but  read  RTC  device  until alarm time
                 appears. This mode is useful for debugging.

Suspend Until A Known Time

A script (at the bottom of this post) could be used to suspend your computer and wake at a specific time:

syntax is suspend_until [hh:mm] for example

sudo ./suspend_until 07:30

Save the script as the name suspend_until and give it execute rights i.e.

chmod +x suspend_until

suspend_until script


# Auto suspend and wake-up script
# Puts the computer on standby and automatically wakes it up at specified time
# Written by Romke van der Meulen <>
# Minor mods fossfreedom for AskUbuntu
# Takes a 24hour time HH:MM as its argument
# Example:
# suspend_until 9:30
# suspend_until 18:45

# ------------------------------------------------------
# Argument check
if [ $# -lt 1 ]; then
    echo "Usage: suspend_until HH:MM"

# Check whether specified time today or tomorrow
DESIRED=$((`date +%s -d "$1"`))
NOW=$((`date +%s`))
if [ $DESIRED -lt $NOW ]; then
    DESIRED=$((`date +%s -d "$1"` + 24*60*60))

# Kill rtcwake if already running
sudo killall rtcwake

# Set RTC wakeup time
# N.B. change "mem" for the suspend option
# find this by "man rtcwake"
sudo rtcwake -l -m mem -t $DESIRED &

# feedback
echo "Suspending..."

# give rtcwake some time to make its stuff
sleep 2

# then suspend
# N.B. dont usually require this bit
#sudo pm-suspend

# Any commands you want to launch after wakeup can be placed here
# Remember: sudo may have expired by now

# Wake up with monitor enabled N.B. change "on" for "off" if 
# you want the monitor to be disabled on wake
xset dpms force on

# and a fresh console
echo "Good morning!"


You can create a root cron job that calls this script to execute at a specific time in the evening and then awake in the morning:

sudo crontab -e

Now enter something like to run the suspend script at 23:30:

30 23 * * * /home/myhomefolder/suspend_until 07:30


Change mem in this part of the script for whatever suspend method works for you:

# Set RTC wakeup time
sudo rtcwake -l -m mem -t $DESIRED &

You may also have to substitute the -u flag in place of the -l flag depending on whether your hardware clock uses UTC (-u) or local (-l) time. Note that your hardware clock is different from the system clock you see in your operating system.

If you want, you can convert this into python script impoting os.system as usual.

Source: askubuntu

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It's not Ubuntu that directly supports this facility.

The BIOS needs to have the right feature.

This page describes that feature

So unless you BIOS supports it, all the commands in the world isn't going to help.

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