Good afternoon.
Is there any function to do commands before device is rebooted?
I don’t know if it is even posible 
No, there is no event “on reboot”, so you can’t run script when router is rebooted.
I don’t know if this will help, but the scheduler can run a script on bootup. Set the script “start-time=Startup”. Maybe if you can be more specific about what you are trying to do at reboot…
FYI: Do not count on the system clock at this point. If the NTP server does not respond right away, it could be still set to the default value.
Thank you mrz. My boss wants a script that monitors users and their changes on devices. Script sends log informations if the user was log off. The problem was if the device will be rebooted, but now I think script can send log informations after start