On Debian (and most Linux systems), the wall command sends a message to all logged-in users. However, by default, it does not display messages on the login prompts (like the tty1 console or getty sessions) because those are not considered "logged-in" sessions.

To ensure your wall message also appears on the login prompts (e.g., Debian GNU/Linux 13 debian tty1 and the login:/password: prompts), you need to configure the system to allow messages to be sent to all terminals, including those managed by getty or agetty.

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Solution: Use mesg and wall with tty Broadcast

1. Enable messages on all TTYs: By default, some TTYs (like /dev/tty1) may have message reception disabled. You can enable it with:

   bash
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   sudo mesg y /dev/tty*

   This allows all TTYs to receive broadcast messages.

2. Send the message with wall: Use the wall command as usual:

   bash
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   echo "Your message here" | wall

   This will now also appear on the login prompts if mesg is enabled.

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Alternative: Use pam_wall (PAM Module)

If you want login prompts to always show system messages (e.g., for maintenance notifications), you can configure PAM (Pluggable Authentication Modules) to display a custom message before login.

1. Edit the PAM configuration: Open /etc/pam.d/login and add:

   text
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   session optional pam_wall.so

   This will display the contents of /etc/issue (or a custom file) before the login prompt.

2. Edit /etc/issue: Add your message to /etc/issue (e.g., echo "System maintenance at 2 AM" | sudo tee /etc/issue).

3. Restart getty: Restart the console service (e.g., systemctl restart getty@tty1).

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Temporary Workaround: Write Directly to TTY

If you want to send a message immediately to all TTYs (including login prompts), you can write directly to each TTY device:

bash
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echo "Your message here" | sudo tee /dev/tty*

This forces the message to appear on all active TTYs, including login prompts.

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Which Method to Use?

• For one-time messages, use mesg y /dev/tty* + wall.
• For persistent login messages, use pam_wall + /etc/issue.
• For immediate broadcast, use tee /dev/tty*.