Which version of node and npm do you have installed? What does it print when you send: node -v and npm -v?

the node version is : v4.2.1 npm version is : 2.14.7

Ok. Node.js and NPM has been installed properly. Now can you run these commands again? http://bit.ly/1p6TWWT

Sorry but I get again the warning when trying to install UI : pi@raspberrypi:~ $ node -vv4.2.1pi@raspberrypi:~ $ npm -v2.14.7pi@raspberrypi:~ $ sudo npm cache cleanpi@raspberrypi:~ $ sudo npm update -g –unsafe-perm node-redpi@raspberrypi:~ $ sudo npm install -g node-red-contrib-uinpm WARN unmet dependency /usr/local/lib/node_modules/npm/node_modules/request/node_modules/http-signature/node_modules/sshpk requires assert-plus@’>=0.2.0 <0.3.0′ but will loadnpm WARN unmet dependency /usr/local/lib/node_modules/npm/node_modules/request/node_modules/http-signature/node_modules/assert-plus,npm WARN unmet dependency which is version 0.1.5npm WARN unmet dependency /usr/local/lib/node_modules/npm/node_modules/request/node_modules/http-signature/node_modules/sshpk/node_modules/dashdash requires assert-plus@’^0.2.0′ but will loadnpm WARN unmet dependency /usr/local/lib/node_modules/npm/node_modules/request/node_modules/http-signature/node_modules/assert-plus,npm WARN unmet dependency which is version 0.1.5node-red-contrib-ui@1.2.19 /usr/local/lib/node_modules/node-red-contrib-ui├── serve-static@1.10.2 (escape-html@1.0.3, parseurl@1.3.1, send@0.13.1)└── socket.io@1.4.5 (debug@2.2.0, has-binary@0.1.7, socket.io-parser@2.2.6, socket.io-adapter@0.4.0, engine.io@1.6.8, socket.io-client@1.4.5)  

Ok, I think I know what the problem is… I think it’s because I’ve recommend installing Node-RED UI globally and it’s trying to pickup some old node modules from the previous Node.js installation. Can you please run these new set of commands: http://bit.ly/1Tbd94e

Sorry, but at reboot it still failed to start Node-RED graphical event wiring tool

Did it install Node-RED UI (no errors)? Run in your terminal and copy exactly what it prints: node-red-start 

And if you go to your browser and enter, can you see the UI? http://YOUR_RPi_IP_ADDRESS:1880/ui

print of node-red-start : pi@raspberrypi:~ $ sudo node-red-start Start Node-RED Once Node-RED has started, point a browser at http://192.168.1.71:1880On Pi Node-RED works better with the Iceweasel browser Use node-red-stop to stop Node-REDUse node-red-start to start Node-RED againUse sudo systemctl enable nodered.service to autostart Node-RED at every bootUse sudo systemctl disable nodered.service to disable autostart on boot To find more nodes and example flows – go to http://flows.nodered.orgYou may also need to install and upgrade npm sudo apt-get install npm sudo npm i -g npm@2.x Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….nodered.service start request repeated too quickly, refusing to start.Failed to start Node-RED graphical event wiring tool..Unit nodered.service entered failed state.Starting Node-RED graphical event wiring tool….Started Node-RED graphical event wiring tool../usr/bin/env: node-red-pi: No such file or directorynodered.service: main process exited, code=exited, status=127/n/aUnit nodered.service entered failed state.nodered.service holdoff time over, scheduling restart.Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….Started Node-RED graphical event wiring tool../usr/bin/env: node-red-pi: No such file or directorynodered.service: main process exited, code=exited, status=127/n/aUnit nodered.service entered failed state.nodered.service holdoff time over, scheduling restart.Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….Started Node-RED graphical event wiring tool../usr/bin/env: node-red-pi: No such file or directorynodered.service: main process exited, code=exited, status=127/n/aUnit nodered.service entered failed state.nodered.service holdoff time over, scheduling restart.Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….Started Node-RED graphical event wiring tool../usr/bin/env: node-red-pi: No such file or directorynodered.service: main process exited, code=exited, status=127/n/aUnit nodered.service entered failed state.nodered.service holdoff time over, scheduling restart.Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….Started Node-RED graphical event wiring tool../usr/bin/env: node-red-pi: No such file or directorynodered.service: main process exited, code=exited, status=127/n/aUnit nodered.service entered failed state.nodered.service holdoff time over, scheduling restart.Stopping Node-RED graphical event wiring tool….Starting Node-RED graphical event wiring tool….nodered.service start request repeated too quickly, refusing to start.Failed to start Node-RED graphical event wiring tool..Unit nodered.service entered failed state. It is not possible to start ui

Did the commands with wget ran successfully? I’m currently flashing a new microSD card to see if I can reproduce this error in my end and fix it. Thanks for the patience! 

Yes the wget commands ran successfully. Anyway, thank’s for the help.

You’re welcome, I’m here to help :). I’m almost 100% sure this will fix the issue and this is the right set of commands, can you try them and give me your feedback?: http://bit.ly/1S1aDhU

You are right There is no more warning. it works. Thank’s a lot    

Awesome! Thanks for letting me know it works 🙂 I’ve updated the Unit! 

I had similar issues and discovered they were related to the systemd startup script for Node-RED, namely: /lib/systemd/system/nodered.service Within that file you will see that it will launch the daemon with user pi and group pi. Since I always remove those user and group in my Raspbian installs, systemd was trying to launch nodered as a service invoking a non-existent UID/GID. I have changed the nodered.service with the correct user and group and now the daemon starts correctly. Ciao, Luca