docs: add Ubuntu screen and systemd deployment guide

README.md

@@ -128,10 +128,13 @@ Logs are written to both the console and `logs/bot.log`. File logs rotate daily,
 and the latest 30 rotated files are retained. Original Telegram message text and
 bot tokens are not logged.
 
-## Simple Deployment on Ubuntu 24.04
+## Deployment on Ubuntu 24.04
 
-This demo deployment runs the bot inside a GNU `screen` session. It does not set
-up automatic restarts or other production infrastructure.
+### Simple screen run
+
+This option runs the bot manually inside a GNU `screen` session under a regular
+Linux user. It is simple and lets you reconnect to the bot session, but it does
+not start the bot automatically after a server reboot.
 
 Install the required system packages:
 
@@ -140,9 +143,10 @@ sudo apt update
 sudo apt install -y git python3 python3-venv screen
 ```
 
-Clone and configure the project:
+Clone and configure the project in the regular user's home directory:
 
 ```bash
+cd ~
 git clone https://github.com/deKibi/codex-time-bot.git
 cd codex-time-bot
 python3 -m venv .venv
@@ -153,13 +157,22 @@ cp .env.example .env
 nano .env
 ```
 
+Check the project path. This is only an example path to the cloned GitHub
+repository; replace it with the actual path on your server where needed:
+
+```bash
+pwd
+# Example output:
+# /home/denys/codex-time-bot
+```
+
 Start a named `screen` session:
 
 ```bash
 screen -S codex-time-bot
 ```
 
-Inside the session, activate the environment and start the bot:
+Inside the `screen` session, start the bot:
 
 ```bash
 source .venv/bin/activate
@@ -169,5 +182,80 @@ python main.py
 Useful `screen` controls:
 
 - Detach while keeping the bot running: press `Ctrl+A`, then `D`.
-- Reconnect: `screen -r codex-time-bot`.
+- Reconnect to the bot session: `screen -r codex-time-bot`.
+- List sessions: `screen -ls`.
 - Stop the bot after reconnecting: press `Ctrl+C`.
+
+### Run as a systemd service
+
+Use this option when the bot should start together with the system and restart
+after crashes. This example still starts the bot inside `screen`, so you can
+reconnect to the running session.
+
+First complete the setup from the simple `screen` run section above. Then create
+a `systemd` service file:
+
+```bash
+sudo nano /etc/systemd/system/codex-time-bot.service
+```
+
+Example service configuration:
+
+```ini
+[Unit]
+Description=Codex Time Bot
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=simple
+User=denys
+WorkingDirectory=/home/denys/codex-time-bot
+Environment=PYTHONUNBUFFERED=1
+ExecStart=/usr/bin/screen -DmS codex-time-bot /home/denys/codex-time-bot/.venv/bin/python main.py
+ExecStop=/usr/bin/screen -S codex-time-bot -X quit
+Restart=on-failure
+RestartSec=5
+
+[Install]
+WantedBy=multi-user.target
+```
+
+In this example, `denys` is the regular Linux user that runs the bot, and
+`/home/denys/codex-time-bot` is only an example project path. Replace `User`,
+`WorkingDirectory`, and the path in `ExecStart` with your actual values.
+
+Enable and start the service:
+
+```bash
+sudo systemctl daemon-reload
+sudo systemctl enable codex-time-bot
+sudo systemctl start codex-time-bot
+```
+
+Check service status:
+
+```bash
+sudo systemctl status codex-time-bot
+```
+
+Useful service commands:
+
+```bash
+sudo systemctl stop codex-time-bot
+sudo systemctl restart codex-time-bot
+sudo journalctl -u codex-time-bot -f
+```
+
+To reconnect to the service-owned `screen` session:
+
+```bash
+screen -r codex-time-bot
+```
+
+Detach with `Ctrl+A`, then `D`. Stop the service through `systemd` instead of
+pressing `Ctrl+C` inside the session:
+
+```bash
+sudo systemctl stop codex-time-bot
+```