Installing manually
The generic setup instructions boil down to

1. Installing Python 3, including pip.
2. Creating a virtual environment somewhere: python -m venv OctoPrint
3. Installing OctoPrint into that virtual environment: OctoPrint/bin/pip install OctoPrint
4. OctoPrint may then be started through ./OctoPrint/bin/octoprint serve or with an absolute path /path/to/OctoPrint/bin/octoprint serve

This starts it up manually

/path/to/OctoPrint/bin/octoprint serve

https://community.octoprint.org/t/setting-up-octoprint-on-a-raspberry-pi-running-raspbian-or-raspberry-pi-os/2337

Basic Installation

cd ~
sudo apt update
sudo apt install python3-pip python3-dev python3-setuptools python3-venv git libyaml-dev build-essential
mkdir OctoPrint && cd OctoPrint
python3 -m venv venv
source venv/bin/activate

OctoPrint and it's Python dependencies can then be installed using pip:

pip install pip --upgrade
pip install octoprint

Note

If this installs an old version of OctoPrint, pip probably still has something cached. In that case add --no-cache-dir to the install command, e.g.

pip install --no-cache-dir octoprint
To make this permanent, clean pip's cache:

rm -r ~/.cache/pip

Starting the server for the first time

pi@raspberrypi:~ $ ~/OctoPrint/venv/bin/octoprint serve
2020-11-03 17:39:17,979 - octoprint.startup - INFO - ***************************
2020-11-03 17:39:17,980 - octoprint.startup - INFO - Starting OctoPrint 1.4.2
2020-11-03 17:39:17,980 - octoprint.startup - INFO - ***************************

Automatic start up

Download the init script files from OctoPrint's repository, move them to their respective folders and make the init script executable:

wget https://github.com/OctoPrint/OctoPrint/raw/master/scripts/octoprint.service && sudo mv octoprint.service /etc/systemd/system/octoprint.service

Adjust the paths to your octoprint binary in /etc/systemd/system/octoprint.service. If you set it up in a virtualenv as described above make sure your
/etc/systemd/system/octoprint.service looks like this:

ExecStart=/home/pi/OctoPrint/venv/bin/octoprint

Then add the script to autostart using sudo systemctl enable octoprint.service.

This will also allow you to start/stop/restart the OctoPrint daemon via

sudo service octoprint {start|stop|restart}