Science and technology

Serial communication on fashionable Linux

As a programs engineer, I spend a whole lot of time in information facilities configuring servers and different pc tools. Two of the objects I maintain in my toolkit are an RS-232 serial-to-USB converter and a normal DB-9 serial cable. These may be indispensable when you haven’t any different option to entry a tool. You might have to deploy a brand new router that has not but been configured in your community. You would possibly have to troubleshoot a firewall equipment that has grow to be inaccessible by way of SSH. In a “lights-out” setting, specifically, new servers might have a administration card that must be initialized. A serial connection gives a direct path to a console for conducting these duties.

I’ll use a Netgate equipment on this instance. These are firewalls that haven’t any mouse, keyboard, monitor, or different GUI capabilities. They’re usually known as “headless.”

Serial communications

To join with a tool over serial, you want hardware that helps the RS-232 protocol. This is often a nine-pin DB-9 serial port, usually labeled serial, comm, or console. Most older computer systems have at the least one. Most servers nonetheless have them, however most laptops and desktops do not any longer.

Find the serial port

If your system does not have already got a serial port, you will want to make use of a converter just like the one I discussed. When you plug within the PL2303 converter to a USB port in your pc, the Linux kernel registers it as a USB TTY system.

There are a number of instructions that you should utilize to question your system for its serial port configuration. Here are just a few examples:

# dmesg |grep tty
[252464.891372] usb 6-1: pl2303 converter now hooked up to ttyUSB0

# setserial -g /dev/ttyUSB[0123]
/dev/ttyUSB0, UART: 16654, Port: 0x0000, IRQ: zero

# ls /dev/serial/by-id/

In my case, it detects the converter as a pl2303 converter (or a Prolific Technology USB serial controller).

Connect a serial cable

Connect your serial cable between the converter and the serial port on the system.

Log in with Tio

Over the years, I’ve used completely different instruments, resembling Minicom and Screen. Tio is a more recent and less complicated device described as “a simple TTY terminal I/O application.” It is accessible on most Linux distributions, FreeBSD, and OpenWRT, in addition to a Snap bundle. I used the usual bundle device to put in model 1.32 onto my Red Hat Enterprise Linux eight.1 server:

# dnf information tio
# dnf set up tio

Initialize the reference to the tio command. In my expertise, Tio did not want any advance configuration; it labored out of the field. Be certain that you’ve the right system path, as proven above:

# tio /dev/ttyUSB0

# tio /dev/serial/by-id/usb-Prolific_Technology_Inc._USB-Serial_Controller_D-if00-port0

You can use the Ctrl+t command sequence to work together with Tio. For occasion, Ctrl+t+? will checklist obtainable instructions, and Ctrl+t+q quits Tio and takes you again to your Linux command immediate.


We hardly ever take into consideration and even use serial communications lately, however it’s nonetheless helpful. Data middle individuals nonetheless should be accustomed to it.

Data facilities may be distant, and as soon as inside, you will wish to be sure you have all the correct instruments. Besides a superb Linux laptop computer, after all, I like to recommend the objects above for managing these serial-enabled gadgets when essential.

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