Use rtcwake without entering a password

Question

I would like to execute something like rtcwake -m off -s 60 without entering a password.

I used visudo to write the following line into /etc/sudoers: %sudo ALL = NOPASSWD: /sbin/shutdown, /sbin/poweroff, /sbin/halt, /sbin/reboot

Now I can shutdown without entering a password. However, using rtcwake without password does not work. Instead, I get the following message:

rtcwake: assuming RTC uses UTC ... rtcwake: wakeup from "off" using /dev/rtc0 at Fri Dec 18 17:45:43 2015 shutdown: Need to be root

What is missing?

Answer 1

Since you're already trusting the user to shut down the system at any time, let them call rtcwake as root. Run visudo and add /usr/sbin/rtcwake to the line with /sbin/shutdown and so on.

Answer 2

You can create a new udev rule to achieve that.

Create a new 40-rtc-permissions.rules file in /lib/udev/rules.d or /etc/udev/rules.d (depending on your distro) where you can put the following line

KERNEL=="rtc0", GROUP="wheel"

Group doesn't have to be wheel. It can be whichever user group you want to have access to the rtc0 device.

Answer 3

Got it. I added the following line to /etc/rc.local:

sudo chmod ugo+r rtc0

and with %sudo ALL = NOPASSWD: /sbin/shutdown, /sbin/poweroff, /usr/sbin/rtcwake in /etc/sudoers. Note that I do not care about security because my application is running on a dedicated computer which does not run critical tasks.

edit: included /usr/sbin/rtcwake in /etc/sudoers according to Gilles answer.