Hello,
I installed this image: 
as I was doing my integrations I followed the steps here
When I restart everything, I get this error stating that the serial port is not open.
so I went back to the arduino page and ran this command: $ sudo usermod -a -G dialout,lock $USER
then got an error about the sudo command not being found.
I then removed the sudo and got an error that the usermod command wasn't found.
So, my simple question is, what command do I use to open this port so I can use it? This is absolutely frustrating. It seems like there is an entire area locked out which prevents me from doing many things.
Oh, and yes, the firmata sketch is on the arduino.
I uploaded a picture of the different errors. Had to do them on one picture because I was only allowed to upload one picture.
It is clear that you don’t have permissions to write to that port, either when it’s created on the spot.
First it’s to understand what is your installation and how you have admin privileges on that. Then later you might try to create an udev rule, that will define the right permissions to the user you want to.
your post is formatted pretty poorly, but I can tell you are using hassio, based on the fact that you are ssh into “core-ssh” which is an SSH add-on (a docker container running alongside home assistant), and as such, you are NOT in the host OS (not that being in the HOST OS would do you any good).
Hassio runs with privileged access and maps through all hardware, so /dev/ttyACM0 is available to you already. You do NOT need to “open a port”, but rather have a look in the hassio menu at the hardware on your system.
