Temporary failure in name resolution in Python script running during boot or on shutdown

Question

I wrote a Python script which sends any message via Telegram:

#!/opt/anaconda3/bin/python

import asyncio
import telegram
import os
import sys


async def main():
    bot = telegram.Bot(os.environ["TELEGRAM_TOKEN"])
    async with bot:

        #print(await bot.get_me())
        #print((await bot.get_updates())[0])
        await bot.send_message(text=' '.join(sys.argv[1:]), chat_id=MYCHATID)


if __name__ == '__main__':
    asyncio.run(main())

TELEGRAM_TOKEN is set in /etc/environment, MYCHATID is hardcoded.

Created two scripts to run it

# cat /etc/init.d/sendbot_boot.sh
#!/bin/bash

/opt/anaconda3/bin/python /usr/local/bin/sendbot "Booting..."

# cat /etc/init.d/sendbot_shutdown.sh
#!/bin/bash

/opt/anaconda3/bin/python /usr/local/bin/sendbot "Shutting down..."

Added one of them to cron

# cat /var/spool/cron/crontabs/root
@reboot /etc/init.d/sendbot_boot.sh

And another one to rc6.

# ls -l /etc/rc6.d/K99sendbot_shutdown
lrwxrwxrwx 1 root root 29 фев 10 02:08 /etc/rc6.d/K99sendbot_shutdown -> ../init.d/sendbot_shutdown.sh

All scripts are executable and work well when I run them from terminal. But neither of them work on actual reboot.

What I did wrong?

# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 18.04.6 LTS
Release:        18.04
Codename:       bionic

---

I have grabbed error output and got:

Traceback (most recent call last):
  File "/opt/anaconda3/lib/python3.8/site-packages/httpcore/_exceptions.py", line 10, in map_exceptions
    yield
  File "/opt/anaconda3/lib/python3.8/site-packages/httpcore/backends/asyncio.py", line 111, in connect_tcp
    stream: anyio.abc.ByteStream = await anyio.connect_tcp(
  File "/opt/anaconda3/lib/python3.8/site-packages/anyio/_core/_sockets.py", line 189, in connect_tcp
    gai_res = await getaddrinfo(
  File "/opt/anaconda3/lib/python3.8/site-packages/anyio/_core/_sockets.py", line 496, in getaddrinfo
    gai_res = await get_asynclib().getaddrinfo(
  File "/opt/anaconda3/lib/python3.8/site-packages/anyio/_backends/_asyncio.py", line 1754, in getaddrinfo
    result = await get_running_loop().getaddrinfo(
  File "/opt/anaconda3/lib/python3.8/asyncio/base_events.py", line 825, in getaddrinfo
    return await self.run_in_executor(
  File "/opt/anaconda3/lib/python3.8/concurrent/futures/thread.py", line 57, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/opt/anaconda3/lib/python3.8/socket.py", line 918, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -3] Temporary failure in name resolution

Answer 1

It looks like the scripts are not executing properly on reboot. On Ubuntu 18.04, system services and scripts in the /etc/rcX.d/ directories are executed with the /sbin/runlevel program. The init scripts in /etc/init.d/ can be executed directly, but they must also be linked to the appropriate /etc/rcX.d/ directory in order to be executed at boot time or when changing runlevels.

Try creating a symlink for your init script in the appropriate rcX.d directory using the following command:

sudo ln -s /etc/init.d/sendbot_boot.sh /etc/rc2.d/S99sendbot_boot
sudo ln -s /etc/init.d/sendbot_shutdown.sh /etc/rc0.d/K99sendbot_shutdown

This should ensure that your scripts are executed on boot and shutdown.

PS: Try to update Ubuntu :-)