Running sudo scripts/bash commands on a remote

Question

I need to remotely start bash scripts that perform sudo tasks, such as chmod and ntpdate and echoing to gpio.

A cron job might be the best solution for some of this, but cron is giving me headaches. I'd like to pass on this venue if I can...

I've confirmed that my scripts work locally (I can ssh into the machine and run them without a hiccup.)

However, If I try to run them remotely like so: (this is within a C++ system call)

ssh user@pc 'bash -s' < /home/user/myScript.sh

Commands with sudo fail.

sudo chmod fails with: no tty present and no askpass program specified echo to gpio fails with: write error: Device or resource busy sudo ntpdate fails with: no tty present and no askpass program specified

Can anyone help explain, or help me determine whats happening here?

I'm open to band-aids and different approaches, thanks!

Answer 1

You already found the problem yourself:

sudo chmod fails with: no tty present and no askpass program specified

If you run you shell script via ssh and the script wants to run the command sudo , sudo itself will ask for the users password. But the ssh session is not a tty! How should sudo now prompt for a password and how to get your password?

You can do it if you provide the password in the script ( what makes it very dangerous if someone else can read that script! )

script.sh:

echo "your passwd" | sudo -S

As alternative solution you can run the ssh session with a more privileged user.

ssh privileged_user@pc 'bash -s' < /home/user/myScript.sh

All that comes with some danger. Running all commands from the cript with a more privileged user can also be dangerous!