Make a Python program a daemon and run it automatically when the OS starts

Until recently, I used to daemonize a slackbot program written in Python with python-daemon, but it was troublesome to manage because the program was not automatically executed when the OS started. When I tried using systemd instead of python-daemon, I was able to execute the program automatically when the OS started, so I will show you how to do it.

Execution environment

Windows 10 Home Python 3.7.3 Raspberry Pi OS 10

1. Program example for running slackbot

run.py

import time

from slackbot.bot import Bot
from slacker import Slacker

def main():
    bot = Bot()
    bot.run()

slack = Slacker('Enter API token')
channel_name = 'Enter the name of the channel you want to post a message to'
message = 'Enter the content of the message'

if __name__ =="__main__":
    slack.chat.post_message(channel_name, message, as_user=True) #Post a message at startup
    time.sleep(3) # 'Start request repeated too quickly.'Measures for
    main() #Launch slackbot

slackbot_settings.py

API_TOKEN = 'Enter API token'
DEFAULT_REPLY = 'Enter the message that the bot returns when you don't understand the meaning of the message addressed to the bot'

PLUGINS = ['run.py, slackbot_settings.Program name used other than py
           (Example: slackbot_module)write']

slackbot_module.py

import random
import re

from slackbot.bot import listen_to

morning_greetings = ['Good morning!', 'Nem ...(˘ω˘)']
@listen_to(r'^(good morning|Good morning ~|Good morning)(There is.*)?$')
def morning_greeting(message, fir_word, sec_word):
    message.reply(random.choice(morning_greetings))
    message.react('Enter the English name of the emoji')

afternoon_greetings = ['Hello!', 'Hello']
@listen_to(r'^Hello.*$')
def afternoon_greeting(message):
    message.reply(random.choice(afternoon_greetings))
    message.react('Enter the English name of the emoji')

night_greetings = ['Good evening!', 'Good evening']
@listen_to(r'^Good evening.*$')
def night_greeting(message):
    message.reply(random.choice(night_greetings))
    message.react('Enter the English name of the emoji)')

important point

Be sure to name the file that describes API_TOKEN slackbot_settings.py: 3 Be sure to write time.sleep (3) in run.py ...! The reason will be explained later.

2. File transfer

Transfer the locally created file to the Raspberry Pi. As a security measure, let's set up public key authentication. After setting, start the command prompt or PowerShell and

scp path of file to copy-i Private key file path-p port number username@hostname:Directory name to put the file

Transfer the file with.

3. SSH connection

Ssh connect to the Raspberry Pi from the command line.

ssh -i Private key file path-p port number username@hostname

You can quickly connect to the remote by creating a configuration file called config directly under~ / .ssh /.

Entry example

Host raspi
    User hoge
    HostName raspberrypi
    Port 2222
    IdentityFile ~/.ssh/id_rsa
    IdentitiesOnly yes

In this example

ssh -i ~/.shh/id_rsa -p 2222 hoge@raspberry

Others,

ssh raspi

You can also make an SSH connection with the command.

4. systemd settings

Create a service file under / etc / systemd / system /. This time I want to daemonize run.py, so I will create a file called rund.service (it doesn't matter if the file name is appropriate).

$ sudo nano /etc/systemd/system/rund.service

Write the following settings to rund.service.

rund.service

[Unit]
Description = slackbot daemon

[Service]
Type = simple
Restart = on-failure
ExecStart =Absolute path to Python3 run.Absolute path to py

[Install]
WantedBy = multi-user.target

Since the writing is finished, I will start systemd.

$ sudo systemctl start rund

Don't forget to check if it works! Let's check the status with the following command.

$ sudo systemctl status rund

If ʻActive: active (running)` is displayed, it is OK.

Set the program called run.py, which was daemonized earlier, to be automatically executed when the OS starts.

$ sudo systemctl enable rund

5. Confirmation of automatic startup

Just in case, make sure that it can be started automatically.

$ sudo reboot

After reconnecting, check the status again with the following command.

$ sudo systemctl status rund

As before, if ʻActive: active (running)` is displayed, the setting is complete! !!

If autostart fails and says'Start request repeated too quickly.'

Immediately after starting the OS, the internet connection is not established yet, so even if run.py is executed at that timing, it seems that slackbot fails to start (in my environment, ʻAfter = network.target in the service file). I couldn't even add `). If it fails to start, rund.service will run run.py again. However, because the internet connection is not connected, the startup fails again ... and so on. After investigating, it seems that the automatic start is set to stop if the automatic start fails 5 times and the total time to start run.py for the 6th time is within 10 seconds. As a countermeasure, write time.sleep () in the line before main () so that automatic startup will not be performed 6 times within 10 seconds.

abridgement

if __name__ =="__main__":
    time.sleep(3)
    main()

If you write it like this, it will start automatically.