Tmux and Screen Guide: SSH Session Management

One of the biggest challenges when working on remote servers is SSH connection drops. When the connection is lost, running processes terminate. Tmux and GNU Screen are terminal multiplexers that solve this problem. This guide covers both tools and helps you understand when to use each.

Why Use Tmux or Screen?

When your SSH session drops:

Running build processes stop
Downloads are interrupted
Long-running scripts terminate
Open text editors close

Tmux and Screen keep sessions alive on the server side. Even if your connection drops, processes continue running in the background. When you reconnect, you pick up exactly where you left off.

Tmux is the more modern, actively developed tool. Screen is older and often comes pre-installed. Knowing both is useful.

Installing Tmux

Ubuntu/Debian

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sudo apt update
sudo apt install tmux -y

# Check version
tmux -V

CentOS/AlmaLinux/RHEL

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sudo dnf install tmux -y
# or on older systems
sudo yum install tmux -y

Tmux Basic Usage

Session Management

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# Start a new session
tmux

# Start a named session
tmux new-session -s myproject
# or shorthand
tmux new -s myproject

# Detach from session — processes keep running
# Ctrl+b, then d

# List existing sessions
tmux list-sessions
# or shorthand
tmux ls

# Reattach to a session
tmux attach-session -t myproject
# or shorthand
tmux attach -t myproject

# Attach to the last session
tmux attach

# Kill a session
tmux kill-session -t myproject

# Kill all sessions
tmux kill-server

The Tmux Prefix Key

All tmux commands start with a prefix key. Default prefix: Ctrl+b

After sending the prefix, press the command key:

Command	Description
`Ctrl+b d`	Detach from session
`Ctrl+b c`	Create new window
`Ctrl+b n`	Next window
`Ctrl+b p`	Previous window
`Ctrl+b 0-9`	Switch to numbered window
`Ctrl+b ,`	Rename window
`Ctrl+b &`	Close current window
`Ctrl+b %`	Split vertically (right)
`Ctrl+b "`	Split horizontally (below)
`Ctrl+b arrow keys`	Navigate between panes
`Ctrl+b z`	Toggle pane fullscreen
`Ctrl+b [`	Enter scroll mode
`Ctrl+b ?`	Help screen

Window Management

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# Create a new window inside tmux
# Ctrl+b, then c

# List windows
# Ctrl+b, then w

# Rename window
# Ctrl+b, then ,

# Close window
# Ctrl+b, then &

Pane Management

Panes let you split a single window into multiple terminals.

hljs bash

# Vertical split (side by side)
# Ctrl+b, then %

# Horizontal split (top/bottom)
# Ctrl+b, then "

# Navigate between panes
# Ctrl+b, then arrow keys

# Toggle pane fullscreen
# Ctrl+b, then z

# Close pane
# Ctrl+b, then x

# Resize pane
# Ctrl+b, then Ctrl+arrow keys

Tmux Configuration

Create ~/.tmux.conf to customize tmux:

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nano ~/.tmux.conf

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# Change prefix to Ctrl+a (like Screen)
unbind C-b
set-option -g prefix C-a
bind-key C-a send-prefix

# Enable mouse support
set -g mouse on

# Start window numbering at 1
set -g base-index 1
setw -g pane-base-index 1

# Customize status bar
set -g status-bg colour235
set -g status-fg white
set -g status-left '[#S] '
set -g status-right '%H:%M %d-%b-%y'

# Increase history limit
set -g history-limit 10000

hljs bash

# Reload configuration
tmux source-file ~/.tmux.conf
# or inside tmux:
# Ctrl+b, then :source-file ~/.tmux.conf

GNU Screen Usage

Screen is older than tmux but often comes pre-installed on many systems.

Installing Screen

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# Ubuntu/Debian
sudo apt install screen -y

# CentOS/AlmaLinux
sudo dnf install screen -y

Screen Basic Commands

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# Start a new session
screen

# Start a named session
screen -S myproject

# Detach from session
# Ctrl+a, then d

# List sessions
screen -ls

# Reattach to session
screen -r myproject

# Attach by ID if multiple sessions exist
screen -r 12345.myproject

# Kill a session
# Inside screen: Ctrl+a, then k
# From outside:
screen -X -S myproject quit

Screen Shortcuts

Screen's prefix key is Ctrl+a:

Command	Description
`Ctrl+a d`	Detach from session
`Ctrl+a c`	Create new window
`Ctrl+a n`	Next window
`Ctrl+a p`	Previous window
`Ctrl+a "`	Window list
`Ctrl+a A`	Rename window
`Ctrl+a S`	Horizontal split
`Ctrl+a	`
`Ctrl+a Tab`	Switch between panes
`Ctrl+a [`	Scroll mode
`Ctrl+a ?`	Help

Tmux vs Screen Comparison

Feature	Tmux	Screen
Active development	Yes	No
Vertical split	Yes	Yes (newer versions)
Mouse support	Yes	Limited
Configuration	Powerful	Basic
Pre-installed	No	Often yes
Learning curve	Medium	Low
Scripting support	Excellent	Good

Practical Use Cases

Long-Running Processes

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# Start a new session
tmux new -s build

# Run a long command
make all

# Detach — process continues
# Ctrl+b d

# Check back later
tmux attach -t build

Multi-Panel Server Monitoring

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# Start session
tmux new -s monitoring

# Vertical split
# Ctrl+b %

# Monitor CPU in left pane
htop

# Switch to right pane (Ctrl+b right arrow)
# Monitor disk I/O
iostat -x 2

hljs bash

# Add to ~/.bashrc or ~/.bash_profile
if command -v tmux &> /dev/null && [ -z "$TMUX" ]; then
  tmux attach -t default || tmux new -s default
fi

Use auto-attach carefully. It can conflict with SSH key-based automation on some systems.

Extend tmux with Tmux Plugin Manager (TPM). The tmux-resurrect plugin preserves sessions even across system reboots.

Conclusion

Tmux and Screen are essential tools for remote server management. When running long processes, build tasks, or continuous monitoring commands on REXE servers, these tools ensure your work is safe even if the SSH connection drops. Screen is a simpler starting point for beginners, but Tmux's flexibility and features make it the better long-term choice.

Tmux and Screen Guide: SSH Session Management

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