Difference between devconsole, devtty, and devtty0

Introduction

In a Linux operating system, every hardware device and most software components are represented as files in /dev directory. Three commonly used devices in /dev directory are devconsole, devtty, and devtty0. These devices are essential for debugging and troubleshooting purposes. However, they have different functionalities and can be confusing for beginners. In this article, we will explain difference between devconsole, devtty, and devtty0, their uses, and how to interact with them.

What is Devconsole?

Devconsole is a virtual device file that represents console, which is default terminal on a Linux system. It is also known as kernel console or system console. console is primary interface between user and operating system, where users can input commands and view output. Devconsole is an essential tool for debugging and troubleshooting issues on system. When operating system boots up, it initializes console and writes boot messages to console.

Uses of Devconsole

Devconsole is used for several purposes, including −

• Debugging − Devconsole provides a way to view kernel messages and debug issues during bootup or system operation.

• Recovery − When system fails to boot, console can provide useful information for troubleshooting and recovery.

• Security − Devconsole is useful for securing system by disabling console access from remote or unauthorized users.

How to use Devconsole

To view console output, open a terminal window and run command −

$ sudo tail -f /var/log/messages

This command displays messages written to system log in real-time. Alternatively, you can use command −

$ dmesg

This command displays kernel messages from system log.

What is Devtty?

Devtty is a virtual device file that represents a physical or virtual terminal. A terminal is an input/output device that allows users to interact with operating system by entering commands and viewing output. Devtty is a generic device that represents any terminal on system, whether it is a physical terminal, a virtual terminal, or a serial port.

Uses of Devtty

Devtty is used for several purposes, including −

• Running shell commands − Devtty provides a way to run shell commands and scripts on system.

• Interacting with hardware devices − Devtty is used to communicate with hardware devices, such as modems or serial ports.

• Running graphical user interfaces − Devtty is used to run graphical user interfaces, such as Xorg or Wayland, which require a terminal to display output.

How to use Devtty

To access Devtty, open a terminal window or a virtual console by pressing Ctrl+Alt+F1. This will take you to first virtual console, represented by device file /dev/tty1. You can switch to other virtual consoles by pressing Ctrl+Alt+F2, Ctrl+Alt+F3, etc. To exit a virtual console, press Ctrl+Alt+F7 to return to graphical user interface.

What is Devtty0?

Devtty0 is a virtual device file that represents current terminal, which is terminal that is currently active on system. It is also known as controlling terminal or foreground terminal. Devtty0 is a special device file that is linked to terminal where user logged in or started a shell session.

Uses of Devtty0

Devtty0 is used for several purposes, including −

• Signal handling − Devtty0 is used to handle signals sent to terminal, such as interrupt signal (Ctrl+C) or quit signal (Ctrl+).

• Process control − Devtty0 is used to control input/output of foreground processes, such as pausing or resuming their execution.

• Job control − Devtty0 is used to manage foreground and background processes, such as switching between them, suspending them, or bringing them to foreground.

How to use Devtty0

To access Devtty0, open a terminal window or a virtual console and run command −

$ tty

This command displays device file name of current terminal, which is usually /dev/tty0. You can also use command −

$ ps -o tty= -p $$

This command displays device file name of terminal where current process is running.

Differences between Devconsole, Devtty, and Devtty0

• Functionality − Devconsole is used to view kernel messages and troubleshoot issues, while Devtty is used to interact with terminals and run shell commands. Devtty0 is used for signal handling, process control, and job control.

• Representation − Devconsole represents default terminal on system, while Devtty represents any terminal on system, and Devtty0 represents current terminal.

• File name − Devconsole is represented by file name /dev/console, Devtty is represented by file names such as /dev/tty1, /dev/tty2, etc., and Devtty0 is represented by file name /dev/tty0.

• Access − Devconsole and Devtty can be accessed by any user on system, while Devtty0 is linked to terminal where user logged in or started a shell session.

Examples

• Debugging − Suppose a Linux system fails to boot. user can access Devconsole to view kernel messages and identify issue.

• Running shell commands − To run a shell command on system, user can open a terminal window and access Devtty by typing commands into terminal.

• Signal handling − Suppose a user wants to interrupt a running process using interrupt signal (Ctrl+C). Devtty0 is used to handle signal and terminate process.

Conclusion

Devconsole, Devtty, and Devtty0 are essential virtual device files in /dev directory of a Linux operating system. Devconsole is used to view kernel messages and troubleshoot issues, Devtty is used to interact with terminals and run shell commands, and Devtty0 is used for signal handling, process control, and job control. While they have different functionalities and uses, they are all crucial for debugging and troubleshooting issues on system. Understanding differences between these devices and their uses is essential for any Linux user or administrator.