Serial Console - Revision history

Randomizedcoder: serial console login

2025-10-28T21:42:18Z

serial console login

← Older revision		Revision as of 21:42, 28 October 2025
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	In this case fixing the terminal size can be achieved by pressing R.		In this case fixing the terminal size can be achieved by pressing R.

			== Serial Console Login ==
			There is a long thread here: https://github.com/NixOS/nixpkgs/issues/84105

			This configuration seems to work<syntaxhighlight lang="nix">
			#
			# serial-tty.nix
			#
			# Serial console configuration for /dev/ttyS0
			# Enables login via serial interface

			# https://github.com/NixOS/nixpkgs/blob/nixos-unstable/nixos/modules/services/ttys/getty.nix
			# https://github.com/NixOS/nixpkgs/issues/84105

			{ config, lib, pkgs, ... }:

			{
			# Enable serial console on ttyS0
			boot.kernelParams = [
			"console=ttyS0,115200"
			];

			# Disable the upstream getty module's automatic configuration for serial-getty@
			# This prevents conflicts with our custom configuration
			systemd.services."serial-getty@" = {
			enable = false;
			};

			# Configure our own serial-getty@ttyS0 service
			systemd.services."serial-getty@ttyS0" = {
			enable = true;
			wantedBy = [ "getty.target" ];
			after = [ "systemd-user-sessions.service" ];
			wants = [ "systemd-user-sessions.service" ];
			serviceConfig = {
			Type = "idle";
			Restart = "always";
			Environment = "TERM=vt220";
			ExecStart = "${pkgs.util-linux}/bin/agetty --login-program ${pkgs.shadow}/bin/login --noclear --keep-baud ttyS0 115200,57600,38400,9600 vt220";
			UtmpIdentifier = "ttyS0";
			StandardInput = "tty";
			StandardOutput = "tty";
			TTYPath = "/dev/ttyS0";
			TTYReset = "yes";
			TTYVHangup = "yes";
			IgnoreSIGPIPE = "no";
			SendSIGHUP = "yes";
			};
			};

			# Enable early console output during boot
			#boot.consoleLogLevel = 7; # Show all kernel messages
			boot.initrd.verbose = true; # Show initrd messages
			}

			</syntaxhighlight>

imported>Clerie at 18:34, 17 December 2023

2023-12-17T18:34:19Z

@@ Line 1: / Line 1: @@
 {{expansion}}
 == Connect to serial device ==
@@ Line 21: / Line 12: @@
    screen /dev/ttyS0 115200
 == Use serial interface as TTY ==

imported>Clerie at 18:33, 17 December 2023

2023-12-17T18:33:06Z

← Older revision		Revision as of 18:33, 17 December 2023
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			== Serial devices ==

			Serial devices under NixOS will get expose with the following file names.
			The file names relate to the driver used for the serial interface.

			* <code>/dev/ttyS*</code>
			* <code>/dev/ttyUSB*</code>
			* <code>/dev/ttyACM*</code>

			== Connect to serial device ==

			Most serial console programs require you to specify a serial device and a baud rate.

			=== With <code>tio</code> ===

			tio -b 115200 /dev/ttyS0

			=== With <code>screen</code> ===

			screen /dev/ttyS0 115200

	== Use serial interface as TTY ==		== Use serial interface as TTY ==

imported>Clerie at 18:26, 17 December 2023

2023-12-17T18:26:06Z

← Older revision		Revision as of 18:26, 17 December 2023
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	{{expansion}}		{{expansion}}

			== Use serial interface as TTY ==

			To use a serial device <code>ttyS0</code> as a TTY to log into the device, you have to tell the kernel and you boot loader about the serial configuration.

			An example for GRUB bootloader:

			boot.kernelParams = [ "console=ttyS0,115200n8" ];
			boot.loader.grub.extraConfig = "
			serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1
			terminal_input serial
			terminal_output serial
			";

			== Unprivileged access to serial device ==

			Serial devices under NixOS are created with the group <code>dialout</code> by default.

			All users that are part of the group <code>dialout</code> can access serial devices.

			Add a user to group <code>dialout</code>:

			users.users.<name>.extraGroups = [ "dialout" ];

	== Tips ==		== Tips ==

imported>Mic92 at 17:11, 27 January 2020

2020-01-27T17:11:29Z

← Older revision		Revision as of 17:11, 27 January 2020
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	This will give you the exact invocation for your current terminal size.		This will give you the exact invocation for your current terminal size.

			In case tmux is used an alternative is to add the following snippet to the <code>tmux.conf</code>

			bind R run "echo \"stty columns $(tmux display -p \#{pane_width}); stty rows $(tmux display -p \#{pane_height})\" \| tmux load-buffer - ; tmux paste-buffer"

			In this case fixing the terminal size can be achieved by pressing R.

imported>Samueldr: I can't even into syntax it seems

2020-01-24T21:20:40Z

I can't even into syntax it seems

← Older revision		Revision as of 21:20, 24 January 2020
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	== Tips		== Tips ==

	=== Serial console wrapping		=== Serial console wrapping ===

	The remote serial console has no knowledge of your local console. This means that it will wrap with safe defaults.		The remote serial console has no knowledge of your local console. This means that it will wrap with safe defaults.

imported>Samueldr: Init with serial console wrapping tip

2020-01-24T21:20:19Z

Init with serial console wrapping tip

New page

{{expansion}}

== Tips

=== Serial console wrapping

The remote serial console has no knowledge of your local console. This means that it will wrap with safe defaults.

You can configure the columns/rows of your serial console using <tt>stty</tt>.

In a console sized like yours, e.g. a new tab or tmux window:

$ echo "stty rows $(tput lines) cols $(tput cols)"

This will give you the exact invocation for your current terminal size.