Hello world! Has anyone managed to use the node-red file write node on the Cerbo GX? I am trying to implement a data logger, by writing to a file on the SD card on my Cerbo, and although the write appears to be successful (no error and input of write node written to output), the file is not update…

I’ve had this problem on RPi3 running Venus OS. It was fixed by logging in via ssh, creating an empty file then setting permissions (chmod 777 filename.txt). The default permissions only provide root access which is why node red can’t access the file.

Thanks I have done this, but for some reason the chmod command isn’t working. I checked by setting permissions to various things (e.g. 222 and 766) but when I check the file attributes, they have stayed the same. Here is the SSH sequence: root@einstein:/run/media/mmcblk0p1/logs# chmod 222 testlo…

I have found the below in the Victron documentation for node-red. Using the /data/home/nodered directory allows me to write the files, but I still cannot access teh SD card! See Venus OS Large image: Signal K and Node-RED [Victron Energy] Q1: Write/read file gives "Error: EACCESS: permission deni…

The node red folder would be a better choice for user data. Just curious, what data are you logging? cheers, John [response edited: I’ve realised the Raspberry Pi mount point is ‘/u-boot’, and the Cerbo mount point is different.]

Thanks I am getting an ‘Operation not permitted’ response when trying to chown the file [image] The logging works OK if I use the nodered folder on the Cerbo. I just wanted to put it on the SD to make it portable and also to make sure I didnt run out of space! Thanks again

I am logging data from a domestic system with a small wind turbine, battery storage and (to be added) solar. Only logging hourly and no more than 10 variables, so not a heavy data load.

oops that’s odd. As root a “operation not permitted”. Well maybe because of card failures. I killed one sd-card an a raspi with venusOS. Unfortunately no further ideas from me.

Hello! That is because the SD card is formated as FAT (In my experience Linux can’t change the permisions on this format). You should format the SD as ext4, then change permisions of the directory or the file via “chmod”.

Thanks! I have found a different and much more simple way of achieving what I need. That is to write the files to /data/home/nodered/ and then use Filezilla to transfer them over the LAN to my PC. I will post a reply to my original post to give others a ‘how to’ to implement a simple data logger …

Has anyone developed a data logger for Cerbo GX using node-red

Node-RED

Marc_HD (Marc) 12 February 2025 17:51 5

chown nodered filename.extension
the command above in the directory of the file: filename.extension

have fun

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Has anyone developed a data logger for Cerbo GX using node-red

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