Raspberry PI as a remote serial console
Build a multi-port remote serial console for under $100 with a Raspberry PI and a few USB serial cables:
Parts:
- Raspberry PI
- USB power supply
- USB serial cables
- Devices that require a serial console
Download and install the Raspberry PI OS following these instructions: https://www.raspberrypi.org/downloads/raspberry-pi-os/
Using a keyboard and monitor, log in with the pi username and change the password:
pi@raspberrypi:~ $ passwd
Changing password for pi.
Current password:
New password:
Retype new password:
Password changed
Enable remote ssh access:
pi@raspberrypi:~ $ sudo systemctl enable ssh
Synchronizing state of ssh.service with SysV service script with /lib/systemd/systemd-sysv-install.
Executing: /lib/systemd/systemd-sysv-install enable ssh
pi@raspberrypi:~ $ sudo systemctl start ssh
SSH into the Raspberry PI:
jemurray@mbp-2019:~ $ ssh pi@192.168.86.6
pi@192.168.86.6's password:
Linux raspberrypi 4.19.118+ #1311 Mon Apr 27 14:16:15 BST 2020 armv6l
The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Thu Jul 23 18:58:21 2020 from 192.168.86.248
pi@raspberrypi:~ $
Determine what device the USB serial cable is registered as. Before plugging in the serial cable, look at all the /dev/tty* files:
pi@raspberrypi:~ $ ls /dev/tty*
/dev/tty /dev/tty19 /dev/tty3 /dev/tty40 /dev/tty51 /dev/tty62
/dev/tty0 /dev/tty2 /dev/tty30 /dev/tty41 /dev/tty52 /dev/tty63
/dev/tty1 /dev/tty20 /dev/tty31 /dev/tty42 /dev/tty53 /dev/tty7
/dev/tty10 /dev/tty21 /dev/tty32 /dev/tty43 /dev/tty54 /dev/tty8
/dev/tty11 /dev/tty22 /dev/tty33 /dev/tty44 /dev/tty55 /dev/tty9
/dev/tty12 /dev/tty23 /dev/tty34 /dev/tty45 /dev/tty56 /dev/ttyAMA0
/dev/tty13 /dev/tty24 /dev/tty35 /dev/tty46 /dev/tty57 /dev/ttyprintk
/dev/tty14 /dev/tty25 /dev/tty36 /dev/tty47 /dev/tty58
/dev/tty15 /dev/tty26 /dev/tty37 /dev/tty48 /dev/tty59
/dev/tty16 /dev/tty27 /dev/tty38 /dev/tty49 /dev/tty6
/dev/tty17 /dev/tty28 /dev/tty39 /dev/tty5 /dev/tty60
/dev/tty18 /dev/tty29 /dev/tty4 /dev/tty50 /dev/tty61
Plug in the serial console cable and look at the /dev/tty* files again. There is a new file: /dev/ttyUSB0, this is the file we are looking for:
pi@raspberrypi:~ $ ls /dev/tty*
/dev/tty /dev/tty19 /dev/tty3 /dev/tty40 /dev/tty51 /dev/tty62
/dev/tty0 /dev/tty2 /dev/tty30 /dev/tty41 /dev/tty52 /dev/tty63
/dev/tty1 /dev/tty20 /dev/tty31 /dev/tty42 /dev/tty53 /dev/tty7
/dev/tty10 /dev/tty21 /dev/tty32 /dev/tty43 /dev/tty54 /dev/tty8
/dev/tty11 /dev/tty22 /dev/tty33 /dev/tty44 /dev/tty55 /dev/tty9
/dev/tty12 /dev/tty23 /dev/tty34 /dev/tty45 /dev/tty56 /dev/ttyAMA0
/dev/tty13 /dev/tty24 /dev/tty35 /dev/tty46 /dev/tty57 /dev/ttyprintk
/dev/tty14 /dev/tty25 /dev/tty36 /dev/tty47 /dev/tty58 /dev/ttyUSB0
/dev/tty15 /dev/tty26 /dev/tty37 /dev/tty48 /dev/tty59
/dev/tty16 /dev/tty27 /dev/tty38 /dev/tty49 /dev/tty6
/dev/tty17 /dev/tty28 /dev/tty39 /dev/tty5 /dev/tty60
/dev/tty18 /dev/tty29 /dev/tty4 /dev/tty50 /dev/tty61
Install the cu utility. This command will be used to connect to the serial console:
pi@raspberrypi:~ $ sudo apt install cu
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
cu
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Connect to the serial console:
pi@raspberrypi:~ $ cu -l /dev/ttyUSB0
Connected.
cisco-sw-home con0 is now available
Press RETURN to get started.
***********************************************************************
* WARNING - Unauthorized access to or use of this system is *
* strictly prohibited. *
* Use of this system is subject to all policies and procedures set *
* forth by the Example Company located at *
* https://example.com/about/compliance-policies. Unauthorized use is *
* prohibited and may result in administrative or legal action. The *
* Example Company may monitor the use of this system. *
***********************************************************************
User Access Verification
Username:
To exit out of the serial console type (two tildes and a period). If you only use one tilde it will drop the SSH session to the Raspberry PI:
<enter>~~.
Multiple USB serial cables can be attached to the Raspberry PI:
pi@raspberrypi:~ $ ls -al /dev/ttyUSB*
crw-rw---- 1 root dialout 188, 0 Jul 23 18:58 /dev/ttyUSB0
crw-rw---- 1 root dialout 188, 1 Jul 23 19:00 /dev/ttyUSB1
Change the options to the cu command to connect to the other serial ports:
cu -l /dev/USB1
Connected.
cisco-sw-home con0 is now available
Press RETURN to get started.
By default the serial speed is 9600bps, this can be adjusted with the -s option, for example 115,200bps:
pi@raspberrypi:~ $ cu -s 115200 -l /dev/ttyUSB0
Connected.