Console Output and Serial Terminals

Overview

This page describes different methods for setting up a serial console post booting up an NST system. See Getting Started - Server Boot for setting up a serial console initially during a NST Live boot.

Serial Console On NST 2.13.0

Add Serial Console On Device: /dev/ttyS0

Use the following command to manually enable the serial console on NST versions 2.13.0 using upstart. This example will set the serial baud rate to: "57600" and use serial device: "/dev/ttyS0".

[root@probe ~]# initctl emit --no-wait fedora.serial-console-available ttyS0 57600

[root@probe ~]# 

A user login prompt should now be active on serial device: "/dev/ttyS0".

Serial Console On NST 2.15.0 or Above

systemctl Bash Completion

The bash shell's completion function can be extended to external programs. The systemd-units RPM package contains a bash completion script ("/etc/bash_completion.d/systemctl-bash-completion.sh") for the systemctl command. To enable it, source it in within your bash shell:

[root@probe ~]# . /etc/bash_completion.d/systemctl-bash-completion.sh

[root@probe ~]# 

To use it, lets say to get the status of a serial device (systemctl status serial-getty@ttyS0.service), perform the following:

systemctl stat<tab>

Substitute the "<tab>" for the tab key. This will result in:

systemctl status

Now the next part of the command:

systemctl status seria<tab>

Again substitute the "<tab>" for the tab key. This will result in the full command:

systemctl status serial-getty@ttyS0.service

***Note: If more than one completion value is found, the hitting the table key will not complete. Use the <esc>+= key sequence (i.e., The Escape key followed by the Equal Sign key) to find out the possible completion values.

Add Serial Console On Device: /dev/ttyS0

Use the following command to manually enable the serial console on NST versions 2.15.x or above using systemd. This example will use the current baud rate (agetty -s option) set typically during a boot time and use serial device: "/dev/ttyS0". If one needs to adjust the baud rate, send a break character on your communications application to cycle through the baud rate list (i.e., In this example: 115200, 38400 and 9600).

[root@probe ~]# systemctl start serial-getty@ttyS0.service

[root@probe ~]# 

A user login prompt should now be active on serial device: "/dev/ttyS0". To get the serial console status use the systemctl command as follows:

[root@probe ~]# systemctl status serial-getty@ttyS0.service

serial-getty@ttyS0.service - Serial Getty on ttyS0
          Loaded: loaded (/lib/systemd/system/serial-getty@.service)
          Active: active (running) since Tue, 17 May 2011 16:59:56 -0400; 5min ago
        Main PID: 31524 (agetty)
          CGroup: name=systemd:/system/serial-getty@.service/ttyS0
                  └ 31524 /sbin/agetty -s ttyS0 115200 38400 9600
[root@probe ~]# 

Add An Additional Serial Login Device: /dev/ttyUSB0

One can add an additional Serial user login session on a serial device. If your NST system does not have a physical serial port, you can plugin a USB To Serial Converter device for user login. In this example we are adding a USB To Serial Converter which attaches as device: "ttyUSB0". Simply start a serial login on this device as follows:

[root@probe ~]# systemctl start serial-getty@ttyUSB0.service

[root@probe ~]# 

A user login prompt should now be active on serial device: "/dev/ttyUSB0". To get the serial console status for this device use the systemctl command as follows:

[root@probe ~]# systemctl status serial-getty@ttyUSB0.service

serial-getty@ttyUSB0.service - Serial Getty on ttyUSB0
	  Loaded: loaded (/lib/systemd/system/serial-getty@.service)
	  Active: active (running) since Fri, 20 May 2011 21:13:55 -0400; 3min 24s ago
	Main PID: 1273 (agetty)
	  CGroup: name=systemd:/system/serial-getty@.service/ttyUSB0
		  └ 1273 /sbin/agetty -s ttyUSB0 115200 38400 9600
[root@probe ~]#

To make this configuration permanent add the following:

[root@probe ~]# ln -sf /lib/systemd/system/getty@.service /etc/systemd/system/getty.target.wants/getty@ttyUSB0.service

[root@probe ~]# systemctl daemon-reload

[root@probe ~]# systemctl start getty@ttyUSB0.service

[root@probe ~]#