Running scripts with passwordless sudo
Quoted from the page (Ubuntu ):
Shutting Down From The Console Without A Password
Often people want to be able to shut their computers down without requiring a password to do so. This is particularly useful in media PCs where you want to be able to use the shutdown command in the media centre to shutdown the whole computer.
To do this you need to add some cmnd aliases as follows:
Cmnd_Alias SHUTDOWN_CMDS = /sbin/poweroff, /sbin/halt, /sbin/reboot
You also need to add a user specification (at the end of the file after the "%admin ALL = (ALL) ALL" line so it takes effect - see above for details):
<your username> ALL=(ALL) NOPASSWD: SHUTDOWN_CMDS
Obviously you need to replace "<your username>" with the username of the user who needs to be able to shutdown the pc without a password. You can use a user alias here as normal.
Read more: Link - Sudoers - Community Help Wiki