How to avoid password prompt in terminal?

Question

So sometimes my Mac loses its connection to the Internet.

When I'm in front of it physically I can use the terminal and do the following to repair it:

networksetup -setnetworkserviceenabled ethernet off

type my password then:

networksetup -setnetworkserviceenabled ethernet on

and type my password again.

The thing is the machine is hosting several servers and I need them to be running even when I'm not physically present. So I wanted to run a daily script that would do this when I'm not present and be sure the connection is reset at least once a day. But since I haven't figured out a way to include my password in the command line I can't do that.

So my question is: is it possible to do what I described?

Answer 1

Ok, thank you Batman for suggesting to edit the sudoer file. Instead of crontab or launchd to schedule it once a day (which wasn't good enough anyway), I instead wrote that applescript to do it more regularly and so far it seems to be working:

repeat
    repeat
        try
            do shell script "ping -t 15 8.8.8.8"
            exit repeat
        on error
            display notification "Reconnection attempt"
            do shell script "sudo networksetup -setnetworkserviceenabled ethernet off"
            do shell script "sudo networksetup -setnetworkserviceenabled ethernet on"
            delay 9
            display notification "Connection should be established"
        end try
    end repeat
    delay 5
end repeat

I'm adding more details: I exported it as an .app then I edited the .plist of it with the lines:

<key>LSBackgroundOnly</key>
<string>1</string>

To make it invisible when it runs (no dock icon) and finally I made it run on login.

Answer 2

sudo allows you to run a command at an elevated permission level. You can edit the sudoers file by running

sudo visudo

One way to do this is to first add a line to your sudoers file which allows the listed commands to be run without a password. By adding the specific command to your sudoers file, you can allow the desired commands to be run without password. You can do this by entering the following 2 lines to your sudoers file (the file that opens when you run "sudo visudo"):

user ALL=(ALL) NOPASSWD: /usr/sbin/networksetup -setnetworkserviceenabled ethernet on user ALL=(ALL) NOPASSWD: /usr/sbin/networksetup -setnetworkserviceenabled ethernet off

with "user" replaced by your user name.

Then, as your user, to run something at a regular time, you can use crontab

crontab -e

and append the lines:

0 1 * * * sudo networksetup -setnetworkserviceenabled ethernet off && sudo networksetup -setnetworkserviceenabled ethernet on

which will apply this restart at 1 AM every day.

Another solution: Add the commands directly to root's crontab:

sudo -s

crontab -e

Then enter the line

0 1 * * * networksetup -setnetworkserviceenabled ethernet off && networksetup -setnetworkserviceenabled ethernet on

and save and exit.

You may want to put this in some sort of script that notifies you that the network has been successfully restarted (e.g. with an email or something) so that you're sure it worked.

Alternatively, you can use a launchd script.