I want the change the permissions of /dev/ttyACM0 from a script.

I have tried this command:

su -c "chmod -R 777 /dev/ttyACM*" -m "$user".

When I execute the script it is asking for a password. I want run this without being prompted for password.

I tried adding an user in /etc/sudoers, but it doesn't work.

It is a CGI script. It is not working external requests (i.e. from other IPs).

user ALL= (user)  NOPASSWD: /usr/lib/cgi-bin/test.cgi

How can I do change the permissions so that anyone can execute the script from other IP addresses?


You haven't said why the sudo solution doesn't work, but troubleshooting sudo is rather onerous. This test line in /etc/sudoers worked for me

cgiuser ALL = (root) NOPASSWD: /bin/chmod -R 777 /tmp/xxx*

so give it a try. Your /etc/sudoers line would be

user ALL = (root) NOPASSWD: /bin/chmod -R 777 /dev/ttyACM*

and your script would have

/usr/bin/sudo /bin/chmod -R 777 /dev/ttyACM*

Just make sure that the script runs as user, for a cgi script it's probably apache or www-data.

PS: The previous answer is just wrong. Provided that you belong to the sudo group or otherwise have the privileges, sudo su - works perfectly to become root, even if no root password is set. sudo -s is probably better, however. YMMV

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