bcm2835_init: Unable to open /dev/mem: Permission denied

[shooftie]

I know that this is not an issue with this package. I'm not sure where else to start a conversation about getting it working.

I am running this on a Pi and am led to believe that the bcm2835 library needs to be run as root.

Does this mean that I must run node-red as root also? I'm worried that this presents a security issue. I am the only user of the Pi but it makes me reluctant to use it for anything sensitive.

[bpmurray]

The real issue here is that it's based on node-dht-sensor which uses the bcm2835 library which itself requires root access. Probably the simplest solution is to rewrite my node to use the WiringPi library - that can now be initialised without being superuser. However, that will require some free time. I'll see what I can do in the near future. In the meantime, if you run node-red as root, it'll work OK.

[shooftie]

Nice, thanks for that. I was hoping you'd say otherwise but at least I now know.

[bpmurray]

I've tried a bunch of things, and I can get it to work not using the BCM library. However, because of timing issues, there's no way to do it without being root. One possible alternative is to separate out the task to monitor the sensors, writing the data to a file, while the NodeRED part would then only have to read the file.

[bpmurray]

For the time being, I'm closing this as a software limitation. When I get time, I'll redo this using a daemon that provides the information in the background.

[shooftie]

Thanks mate. I've put the RPi away for the time being but will pick it up again in the future for sure...

[TTVert]

Any progress on this? I'm in a weird situation where with my other Pi3 install it worked but on this new install i get the same issue "bcm2835_init: Unable to open /dev/mem: Permission denied" I tried to give that file 777 as a test then I got "bcm2835_init: Unable to open /dev/mem: Operation not permitted 31 Dec 22:50:18 - [error] [rpi-dht22:f5826526.273b68] TypeError: failed to initialize"

Dave

[whatifwhatelse]

got same problem and managed to solved that way : I noticed that bcm2835 release 1.52 solved the problem allowing to use /dev/memgpio instead of /dev/men, thus not requiring root access. so to make node-red-contrib-dht-sensor work i ha d to do this :

uninstall old bcm2835.1.38 (simply remove directory install and make new release 1.52 uninstall node-red-contrib-dht-sensor using : sudo npm uninstall --unsafe-perm -g node-red-contrib-dht-sensor uninstall node-red-dht-sensor using : sudo npm uninstall --unsafe-perm -g node-dht-sensor reinstall both items above using sudo npm install --unsafe-perm -g node-dht-sensor sudo npm install --unsafe-perm -g node-red-contrib-dht-sensor

after these operations, node-red dht node worked perfectly.

[bpmurray]

Thanks for the info - I'll add that to the doc.

[pakair]

installed bcm release 1.52 but I still get errors on sudo npm install -g node-dht-sensor Tried the latest bcm 1.56, still errors on the npm command. Is there a solution?