How to run a command in node-red node exec to enable a script for LCD

[Riyas]

I have a script to bring a current time on LCD in Raspberry PI. LCD is connected with Raspberry PI tested working fine. I created a script name index.js inside ~/.node-red folder, and have installed LCD node module inside the same ~/.node-red folder using command : npm install lcd --save cd ~/.node-red pi@raspberrypi ~/.node-red $ sudo node index.js When I tested inside using the command it brings the time on the LCD. How to execute this index.js script in node-red node exec? I have tried but does not work. node-red connection picture node exec config picture [{"id":"49a533a9.b65acc","type":"inject","name":"","topic":"","payload":"1","payloadType":"string","repeat":"","crontab":"","once":false,"x":127,"y":97,"z":"5acd84ba.a5327c","wires":[["14f033d4.eb0fcc"]]},{"id":"14f033d4.eb0fcc","type":"exec","command":"sudo /home/pi/.node-red/node index.js","addpay":true,"append":"","useSpawn":"","name":"LCD","x":329.18345642089844,"y":107.16499328613281,"z":"5acd84ba.a5327c","wires":[[],[],[]]}] In inject node I entered string 1 as payload In exec node I entered command: sudo /home/pi/.node-red/node index.js I tried in many ways to execute but no luck, please check the pictures and help me in this issue. Thanks a lot in advance

[Dave C-J]

​Well there are a couple of things....

1) the flow has some extra path in the exec node that isn't the same as your command above...​

2) what user are you running Node-RED as ? You can't raise the access (or escalate privileges) by using sudo inside the runtime...

you can either not use sudo in your exec command...  or you can run the whole of Node-RED as sudo .... and then still not run sudo inside that exec :-)

If you need sudo to talk to the LCD then maybe investigate why that needs to be run as root... can you add yourself to some group that has the required privileges ?

Good luck

[Riyas]

Thanks for the reply. i log in as user pi, it is not a root or super user. 

[Dave C-J]

So OK - you can't use sudo in an exec node.

[Riyas]

Hi , if not , is there a different way to execute the script in my case ?

[Dave C-J]

as per my first reply you can either

run Node-RED as root user 

    sudo node-red

or find out why talking to the LCD needs root ... if on a pi - maybe read this and note the bit about the dialout group... http://elinux.org/RPi_Serial_Connection

You should be able to run your app (outside of Node-RED) without using sudo.

[Peter Scargill]

Lets say the only way was to run node-red as root - and you've stuffed all your new nodes in the pi/.node-red directory

How do you move everything so it all still works for the root node-red version....  I'm averse to going this but I'm losing the battle to get gpio access on some non-Pi boards without root.

[Dave C-J]

Peter,

well - two options... 1) you can use the -u userdir param when you call Node-RED to point back to your normal .node-red location...

or 2 - if your gpio command you are exec-ing out to is a real command (and not a shell script) - you can look at setting suid - eg http://www.linuxnix.com/suid-set-suid-linuxunix/ - to set the app to run as root even though you call it as another user...  

(I would go with 2 :-)

[Peter Scargill]

Tried the latter Dave – worked with C program written using WiringOp -  no problem – but that of course does now let me access PWM on non-PI

In this case- made no difference.

 

FAHW-Lib: Unable to open file /sys/class/gpio/gpio203/value

Etc

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[Julian Knight]

What owns the gpio folder? On the pi it is owned by root/gpio

If your non-pi boards own it as root/root, I recommend changing it to something else. Probably create a gpio group and then move the group ownership accordingly. Then the issues should go away. You just need to remember to add the steps to your master config script for when you do a major upgrade or OS reinstall.