Exec node + Python3 Script on Ubuntu resulting in [Errno 13] Permission denied

General
1

Hi all,
New to Node-Red and Ubuntu but I was moving fine ... until i crashed! Hope that you can help me clarify an issue that has been torturing me for a couple of days:

The Intended Flow that is not working: [Inject node] sends “hello…” string → [Exec node] calls Python3 script and passes the payload as parameter - This returns a JSON string → [Debug node] shows the JSON string returned from Exec node.

The issue - Exec node returns permission error:

Command failed: python3 /home/alex/ac_work/python3/p3_test_1.py "Parameter-1"
python3: can't open file '/home/alex/ac_work/python3/p3_test_1.py': [Errno 13] Permission denied

Some facts:
1 - If I go to Terminal and type the command used in the “exec” node, the script runs properly. It takes the parameter and returns the JSON string. No issues.
2 - The directory where the python3 script is at has the following permissions:
alex@alex-FX6860:~/ac_work/python3$ ls -l
total 8
-rw-r--r-- 1 root root 14 Jun 8 20:10 nodered_created_file2.txt
-rwxrwxrw- 1 alex ac_nodered 422 Jun 8 16:15 p3_test_1.py
alex@alex-FX6860:~/ac_work/python3$
3 - I created a simple output to file using the [File node], and the “nodered_created_file2.txt” got created. Notice that it has “root” as both owner and group.
4 - Created a Group called ac_nodered (users alex and root), and this is the Gropu in the directory where the python script resides.
5 - Environment: Node-Red 1.0.6 running on Ubuntu 18.04.4 LTS, and started from the browser as URL http://127.0.0.1:1880/

Why is that this happens when, it appears that Node-RED is executing as root (all the reach of root), and also, root is one of the users in the group ac_nodered that has "rwx" in that directory?

Any help will be greatly appreciated. Rgds,Alex

2

Do you have a good reason for running as root? This is inherently risky as it gives node-red full access to trash your system in the case of a bug, accident or malicious intent.
I would start by fixing that, so it is not running as root (did you see the recommended Debian/Ubuntu/Pi install script?). Then fix the file permissions in your home folder
sudo chown -R alex:alex ~
and start again. This may not fix the problem but may throw light on what is going on.

3

Hi Colin, thanks for your reply. I don't know why Node-Red is using 'root' user, and it was definitely not my intention. I didn't request that during installation of Node-Red.

How can I change the Ubuntu user that is being used by Node-Red to my user "alex"?

Thanks!

4

How did you install it and how are you running it?
Also please post the startup log you get when you run it.

5

Colin, for a clean start, I exported my flows, reinstalled Node-RED in my Ubuntu machine following https://nodered.org/docs/getting-started/raspberrypi, imported flows again, and now everything works properly.
Thank you!

6

Excellent, glad to be of help.

7

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