Serial Console
Connect to serial device
Most serial console programs require you to specify a serial device and a baud rate.
With tio
tio -b 115200 /dev/ttyS0
With screen
screen /dev/ttyS0 115200
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.
/dev/ttyS*
/dev/ttyUSB*
/dev/ttyACM*
Use serial interface as TTY
To use a serial device ttyS0
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 dialout
by default.
All users that are part of the group dialout
can access serial devices.
Add a user to group dialout
:
users.users.<name>.extraGroups = [ "dialout" ];
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 stty.
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.
In case tmux is used an alternative is to add the following snippet to the tmux.conf
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.