Hibernate at certain hours. It's possible?

[Anjunas]

Hello!

I would like to know if it is possible to put the PC into hibernation for a certain period of time, for example, from 01:00 am to 12:00 pm and have it on the rest of the time.

It's possible?

greetings and thanks.

[Snowhog]

This might be helpful: https://www.baeldung.com/linux/auto-suspend-wake

A quick search finds that hibernation isn't enabled in Ubuntu 'by default'. It can be enabled.

[oshunluvr]

As Snowhog points out via link - suspend might allow this. Hibernation would be more difficult. I suspect that waking from Hibernation would require your hardware to support Wake-On-Lan in the BIOS. If that's try, then powering off would make more sense IMO. YOu would need some outside source to send the magic packet for this to work - like a router.

There's good power state info here: https://wiki.archlinux.org/title/Pow..._and_hibernate

[Anjunas]

Hello, thanks for helping.

Sorry to reply so late but I've been busy.

I have tried the following command:

sudo rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+%s')"

And it worked, it went to sleep and at the specific time it turned on again.


But I want this to be done automatically every day. On one of the websites, I saw that Cron can be used. Once inside the cron file I wrote the following:

30 16 * * * rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+%s')

The problem is that nothing happens, it's as if Cron doesn't work. I have looked and cron is activated. But nothing happens.

What am I doing wrong?

Thanks and regards.

[Schwarzer Kater]

Which "cron file" did you use? If you used /etc/crontab did you specify a user? Did you use sudoedit or did you edit for a user?

And possibly there are syntax/logical errors - see e.g. man 5 crontab:

"[…] Percent-signs (%) in the command, unless escaped with backslash (\), will be changed into new-
line characters, and all data after the first % will be sent to the command as standard input. […]"
et al.

And you would be missing an end quote - at least in your post above…

PS:
You could also start a simple shell script with cron which might be easier to debug…
And additionally you could install the cron module for KDE Plasma's System Settings (sudo apt install kde-config-cron) which might be easier to use.

[Anjunas]

I think I edit it as user.

In cron program tasks I appear as a user and not as root.
I have tried clicking execute task now, and it says permission denied. I guess that's where the error lies.

But I don't know how to edit it as root.

PS: to open and edit the file I simply write:

crontab -e

[Schwarzer Kater]

If you need to execute something with elevated privileges or as a specific user, you could use the systemwide crontab in /etc/crontab :

1. sudo systemctl stop cron.service
2. Edit the systemwide crontab with sudoedit /etc/crontab
3. sudo systemctl start cron.service

But don't forget to remove the stuff you added to the user's crontab first.

[Anjunas]

Hello again.

I can't get it to work, I'm doing something wrong hehe.


When I hit run now in the task scheduler, to see if it works it tells me: RTCWAKE: /dev/rtc0/unable to find device: permission deined.

EDIT:
Maybe this command is not correct in cron?

Couse if If I run it in the console it works.

30 16 * * * rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+%s')

I just wanna the computer go to sleep (16:30 pm) and wake up (22:30 pm).

[Snowhog]

IMO, the easiest way to do what you want, is to put the working command (what you did in the konsole) into a bash script, and have the CRON job call that script.

[claydoh]

30 16 * * * rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+%s')

As the black kitty mentioned, your above string is missing a parenthesis at the end, unless you mis-copied it. ......Which looks to be the case, based on the images

You also need to add a backslash ("") before the "%", as he also mentioned, as cron has some little quirks in text string formatting compared to bash.
The "permission denied." indicates sudo may need to be used, even though it is the system cron.

so:
30 16 * * * sudo rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"

Some references

https://yunli.nl/blogs/2020-08-17_wa...e_and_crontab/
https://unix.stackexchange.com/quest...within-crontab

[Snowhog]

30 16 * * * sudo rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"

Given that sudo is being used here, won't that then result in a prompt for the password?

[claydoh]

Given that sudo is being used here, won't that then result in a prompt for the password?

Not for the 'root' cron.

Both my links, and others, seem to confirm that sudo is necessary here.

[Schwarzer Kater]

So either sudo crontab -e (to use the 'root' crontab) and add

[…]
30 16 * * * sudo rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"
[…]

or use the systemwide crontab like I mentioned in post # 7 and add

30 16 * * *    root    rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"

But debugging is easier IMHO if you start a little shell script from either the 'root' crontab with sudo or execute it as root from the systemwide crontab - as Snowhog also wrote.
Also better use absolute paths in crontabs when you start a script.

[Anjunas]

Thank you very much everyone for the help.

I finally got it to work.

I added the root user

I also liked the idea of making a bash. Unfortunately my knowledge is very limited.

Would it be something like that?

sudo nano /home/users/me/myfuction.sh

#!/bin/bash
rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"

sudoedit /etc/crontab

30 16 * * * /home/users/me/myfuction.sh​"

I don't have much idea but would it be like that?

Thank you and greetings.

[Schwarzer Kater]

[…]
I also liked the idea of making a bash. Unfortunately my knowledge is very limited.

Would it be something like that?

sudo nano /home/users/me/myfuction.sh

#!/bin/bash
rtcwake -m mem -l -t "$(date -d 'today 22:30:00' '+\%s')"

You can use Kate to write scripts - it is much more comfortable (at least for me if I have a GUI…).
And the sudo before nano does not belong there (not necessary - in fact I consider it not correct in your case to create a script that belongs to root within your /home directory).


Within the Bash script you should not need the / anymore before the %s.

sudoedit /etc/crontab

30 16 * * * /home/users/me/myfuction.sh​"

I don't have much idea but would it be like that?
[…]

You forgot to specify the user root in field #6 - you want to execute the script with elevated privileges from the systemwide crontab if I understood correctly.
And there is a " too much at the end of the line.
Don't forget to make your script executable with chmod +x /home/users/me/myfuction.sh


Picture:
No sudo necessary if you use the systemwide crontab - you already specified to execute the command as root (in field #6)


PS: Don't forget to stop and start cron.service before and after editing the systemwide crontab (!) - otherwise there is a little chance that unfortunate things could happen if you are unlucky…