I'm trying to use systemd to run a python3 script, it was working fine, however I changed my python script to use the built in OS module as I wanted to retrieve an enviroment variable from the system to use in the python script as a variable.
The python script is as follows:
#/usr/bin/python
import sys, requests, json, time, os
import paho.mqtt.client as mqtt
from requests.auth import HTTPBasicAuth
from datetime import datetime
MQTT_DEVICE_ID = os.environ['DEVICE_ID']+"/DEFENCE"
The DEVICE_ID enviroment variable comes from one I set in /etc/enviroment:
export DEVICE_ID="TEST1"
user@computer:~ $ echo $DEVICE_ID
TEST1
After adding this change to my python script the systemd service that runs this script no longer starts, it will work for a brief period then it will keep failing and thren working again and failing:
computer@computer:~ $ sudo systemctl status mqtt.service
● mqtt_defense.service - Arms the mqtt.py script that will alert if the device is moved
Loaded: loaded (/etc/systemd/system/mqtt.service; disabled; vendor preset: enabled)
Active: activating (auto-restart) (Result: exit-code) since Thu 2022-08-11 08:57:37 BST; 1s ago
Process: 2442 ExecStart=python3 /scripts/mqtt.py (code=exited, status=1/FAILURE)
Main PID: 2442 (code=exited, status=1/FAILURE)
CPU: 631ms
Aug 11 08:57:37 computer systemd[1]: mqtt.service: Main process exited, code=exited, status=1/FAILURE
Aug 11 08:57:37 computer systemd[1]: mqtt.service: Failed with result 'exit-code'.
user@computer:~ $ sudo systemctl status mqtt_defense.service
● mqtt.service - Arms the mqtt.py script that will alert if the device is moved
Loaded: loaded (/etc/systemd/system/mqtt.service; disabled; vendor preset: enabled)
Active: activating (auto-restart) (Result: exit-code) since Thu 2022-08-11 08:57:37 BST; 3s ago
Process: 2442 ExecStart=python3 /scripts/mqtt.py (code=exited, status=1/FAILURE)
Main PID: 2442 (code=exited, status=1/FAILURE)
CPU: 631ms
Aug 11 08:57:37 computer systemd[1]: mqtt.service: Main process exited, code=exited, status=1/FAILURE
Aug 11 08:57:37 computer systemd[1]: mqtt.service: Failed with result 'exit-code'.
user@computer:~ $ sudo systemctl status mqtt.service
● mqtt.service - Arms the mqtt_defense.py script that will alert if the device is moved
Loaded: loaded (/etc/systemd/system/mqtt.service; disabled; vendor preset: enabled)
Active: active (running) since Thu 2022-08-11 08:57:59 BST; 304ms ago
Main PID: 2475 (python3)
Tasks: 1 (limit: 3720)
CPU: 295ms
CGroup: /system.slice/mqtt.service
└─2475 python3 /scripts/mqtt.py
Aug 11 08:57:59 computer systemd[1]: Started Arms the mqtt.py script that will alert if the device is moved.
user@computer:~ $ sudo systemctl status mqtt.service
● mqtt.service - Arms the mqtt.py script that will alert if the device is moved
Loaded: loaded (/etc/systemd/system/mqtt.service; disabled; vendor preset: enabled)
Active: activating (auto-restart) (Result: exit-code) since Thu 2022-08-11 08:58:40 BST; 2s ago
Process: 2551 ExecStart=python3 /scripts/mqtt.py (code=exited, status=1/FAILURE)
Main PID: 2551 (code=exited, status=1/FAILURE)
CPU: 633ms
After reading a few other questions on this issue such as this, I've tried altering my service to add the WorkingDirectory, User and Group as follows:
[Unit]
Description=Runs the mqtt.py script
After=multi-user.target
[Service]
WorkingDirectory=/scripts/
User=user
Group=user
Type=simple
ExecStart=python3 /scripts/mqtt.py
Restart=always
RestartSec=5
TimeoutSec=60
RuntimeMaxSec=infinity
[Install]
WantedBy=multi-user.target
I've also tried changing the User and Group to root, still with no success. If I don't use the OS module in my python script the systemd service runs perfectly.
I have a feeling this is a specific problem with the python OS module or that I'm trying to access etc/enviroment in my python script, but I'm not sure what would be the issue.
Any help would be appreciated, thanks.
This has nothing to do with Python. Your problem is that systemd doesn't expose the env vars defined in /etc/environment by default. See, for example, https://unix.stackexchange.com/questions/473001/env-vars-in-etc-environment-not-globally-visible. As explained in the answer to that question /etc/environment is only loaded by PAM (pluggable authentication module) managed sessions such as interactive logins. AFAIK, systemd doesn't use PAM.