Managing Terminals And Consoles

Understanding Terminals and Consoles

A terminal is a software program that provides text-based access for entering commands and viewing output from the operating system shell, applications, and other command-line interfaces. Common terminal emulators on Linux include xterm, gnome-terminal, konsole, and rxvt. Terminals do not manage their own display and input/output (I/O) streams but rather leverage the display, keyboard, and mouse components managed by the window system or operating system.

A console refers to a system’s text input/output environment provided by the kernel and system hardware. On Linux, there are two types of consoles:

TTY consoles: Text-based virtual consoles managed directly by the kernel to interface with keyboard, display, and mouse without needing the graphical environment or window system
Virtual consoles: Additional TTY consoles configured beyond the first six consoles for increased multi-user access

The main differences between terminals and consoles are:

Terminals emulators run in the user space of an operating system whereas consoles use kernel space and low-level system interactions
Terminals rely on a window system and display server for user interface capabilities while consoles handle input and output streams directly
There can be multiple instances of terminal emulator programs running while typically only one active TTY console is used for login and command interactions

Examples of Common Terminal Emulators

Some of the most common terminal emulator programs on Linux include:

xterm – The standard terminal emulator for the X Window System and the default in many Linux distributions. It provides strong customization support through command line options and resource files.
gnome-terminal – The default terminal for GNOME desktop with features like tabs, profiles, configurable keyboard shortcuts, color schemes, and font options.
konsole – KDE’s terminal emulator with similar tabbing and customization capabilities plus enhanced background transparency effects.
rxvt – A lightweight but featured packed terminal focused on performance and speed written using the RXVT (ouR XVT) emulation library.

Examples of TTY Consoles and Virtual Consoles

The TTY consoles on a Linux system include six text-based consoles accessed by using the Ctrl+Alt+F1 through Ctrl+Alt+F6 key combinations. The graphical desktop is typically on TTY console 7. Any configurations beyond the first six TTY consoles are called virtual consoles. These allow for additional terminal logins.

To verify the current TTY consoles, use:

$ ls /dev/tty[1-6]

To get details on existing virtual consoles:

$ ls /dev/vcs[1-63]
$ ls /dev/vcsa[1-63]

Accessing and Switching Between Consoles

Linux provides robust capabilities for easily accessing and navigating between the various TTY and virtual consoles as well as opening new terminal windows and tabs.

Viewing Available TTY Consoles

The primary TTY consoles accessible using the Ctrl+Alt+F[1-6] key combinations can be listed using:

$ fgconsole
1
$ ps ax | grep tty
pts/0    Ss     0:00 /dev/pts/0 /bin/bash
pts/1    Ss+    0:00 /dev/pts/1 /bin/bash  
tty1     Ss+    0:00 /sbin/agetty -o -p -- \u --noclear tty1 linux
tty2     Ss+    0:00 /sbin/agetty tty2 linux
tty3     Ss+    0:00 /sbin/agetty tty3 linux
tty4     Ss+    0:00 /sbin/agetty tty4 linux
tty5     Ss+    0:00 /sbin/agetty tty5 linux
tty6     Ss+    0:00 /sbin/agetty tty6 linux
tty7     Ss+    0:00 /usr/bin/X -nolisten tcp :0 -auth guess

Switching Between TTY Consoles

Rapid switching between TTY consoles is easily achieved using the following keyboard shortcuts:

Ctrl+Alt+F1 – Switch to tty1
Ctrl+Alt+F2 – Switch to tty2
Ctrl+Alt+F3 – Switch to tty3
Ctrl+Alt+F4 – Switch to tty4
Ctrl+Alt+F5 – Switch to tty5
Ctrl+Alt+F6 – Switch to tty6

To return to the graphical desktop, use Ctrl+Alt+F7.

Launching New Terminal Emulator Windows and Tabs

Within a desktop environment, additional terminal emulator windows and tabs can be easily accessed using any of the following methods:

Running the xterm, gnome-terminal, konsole or other terminal command directly from an existing terminal window’s shell
Navigating through the graphical user interface menus in GNOME, KDE or other desktop environments
Configuring keyboard shortcuts for opening new terminal windows or tabs
Opening files from the File Manager using the right-click context menu on the file

For example, in GNOME desktop environments simply use the keyboard shortcut Ctrl+Alt+T to open a new terminal tab or window. Most terminal emulators provide similar streamlined access mechanisms.

Customizing the Terminal Environment

Linux offers extreme flexibility in tuning the terminal environment to meet specific user needs and preferences through terminal profiles, custom shells, tuned color palettes, diverse font options, scroll buffer adjustments, compatibility settings, advanced clipboard capabilities and more.

Configuring Profiles in Terminal Emulators

Most standard terminal emulators like gnome-terminal, konsole, xfce4-terminal and rxvt-unicode support custom profiles for tailoring terminal preferences and defaults including:

Shell environment – bash, zsh, fish, etc.
Color scheme and palette
Font family and size
Cursor shape and blink mode
Scrollback buffer lines
Encoding compatibility
Background image transparency

These profiles load predefined combinations of settings automatically when opening new terminal windows or tabs. Users can create multiple profiles suited for particular use cases like software development, system administration or entertainment.

Setting the Shell, Color Scheme, Fonts and More

In addition to leveraging profiles, most terminal emulators provide granular control for tuning aspects like:

Shell – Change the shell used for that terminal window’s sessions e.g. bash, zsh, csh, ksh, etc.
Color Scheme – Set custom color palettes, often with ready-made themes available as imports
Fonts – Specify different font families, sizes, hinting and anti-aliasing effects
Scrollback Buffer – Increase or decrease the number of rows held in the terminal’s scrollback history

These settings can be configured through the terminal emulator GUI menus directly for convenience or by editing the emulator’s preferences configuration file manually for more control.

Enabling Copy/Paste, Compatibility Modes

Modern terminal emulators also provide helpful options to enable:

Clipboard access using Ctrl+Shift+C/V shortcuts
Drag and drop of text between windows
Unicode character and symbol support
Legacy encoding modes like IBM/DOS for compatibility needs

These capabilities can improve productivity when working across multiple terminal windows.

Working with Multiple Terminals

Juggling tasks across different terminal sessions is also streamlined in Linux via built-in workflows for organizing tabs/windows in terminal emulators directly and leveraging terminal multiplexers like tmux and screen.

Opening Tabs and Windows in Terminal Emulators

Most standard terminal emulators like gnome-terminal and konsole include native tab management capabilities for splitting a single terminal window into multiple tabs.

Common keyboard shortcuts include:

Ctrl+Shift+T – Open new tab
Ctrl+PageUp/PageDown – Switch between tabs
Ctrl+W – Close current tab

Right-click context menus also provide options for opening new tabs and organizing existing ones. Similarly, additional terminal emulator windows can be launched as needed.

Organizing Sessions with tmux and screen

tmux and screen are terminal multiplexers that enable advanced session management by allowing multiple terminal sessions within a single terminal window or remote SSH connection. Key capabilities include:

Start new named sessions you can attach/detach from
Subdivide sessions into windows and panes
Synchronize sessions across client connections
Scrollback buffer preserved when detaching

For example, you can start a tmux session, open vim and stress testing scripts in different windows, detach safely and pick back up on a different client without losing state.

Attaching and Detaching Remote Sessions

When accessing servers over SSH, tmux/screen allow you to start persistent sessions you can attach/re-attach to later without losing data. The steps would be:

SSH into the remote server
Start a new tmux or screen session
Run tasks like long-running tests, logs and monitors
Detach the multiplexer session safely
SSH back into the server and re-attach the session with its name
Resume working seamlessly

This enables managing long-running processes on remote servers directly from your local client while retaining the full terminal environment.

Administering Consoles Securely

Proper security principles also apply for accessing and managing Linux consoles safely. Admins should limit access with authentication, monitor usage via logs and minimize attack surfaces as with any privileged system resources.

Restricting Access to TTY Consoles

By default all local TTY console logins don’t require authentication on single user systems. But with multiple accounts, best practices suggest strengthening access controls by:

Setting BIOS and bootloader passwords
Enabling single user mode authentication
Requiring login for TTY access in PAM config files like /etc/pam.d/login

This forces users to provide credentials before accessing any available TTY consoles locally.

Setting Authentication for Console Access

In cloud environments, instances often expose virtual consoles over HTTPS for emergency access. These consoles should always be password protected by:

Using SSH keys for primary access instead of passwords
Generating secure HTTPS certificates and consoles credentials
Restricting console access to site reliability engineers only

Role based access controls prevent exposure to wider internal teams or externally.

Logging Console Activity

Monitoring login attempts, commands run and network activity on consoles gives visibility into potential security events. Enable console logging by:

Adding TTY logs to central syslog servers
Journald logging for user sessions on Systemd systems
UFW firewall logs for managing console network rules
Scripting session captures for forensics if needed

Regular log reviews and archival protects against misuse while meeting compliance needs.