screen Quick Reference

Overview

GNU screen is a terminal multiplexer that predates tmux. It allows you to run multiple terminal sessions inside a single window, detach/reattach sessions, and persist sessions across disconnects.

Why screen: - Available on virtually every Unix/Linux system - Lighter weight than tmux - Simple and battle-tested (since 1987) - Default on many legacy servers - Essential for persistent SSH sessions - Serial console access support

Check Version:

screen -v

1. Core Concepts

Session Management

Unlike tmux's three-level hierarchy (session → window → pane), screen has a two-level structure:

screen Session
Window 0: bash
Window 1: vim
Window 2: logs
Window 3: monitoring

Terminology: - Session: A collection of windows that persists after disconnect - Window: A single terminal instance running a command - Command Key: Default Ctrl+a, triggers screen commands - Detach: Disconnect from session (session continues running) - Reattach: Reconnect to detached session

2. Session Management

Create and Attach Sessions

# Start new session
screen

# Start session with name
screen -S mywork

# Start session running a command
screen -S build make build

# List all sessions
screen -ls
# or
screen -list

# Attach to session by name
screen -r mywork

# Attach to session by PID
screen -r 12345

# Attach to only session (if only one exists)
screen -r

# Force attach (disconnect other attached clients)
screen -dr mywork

# Detach from current session (inside screen)
Ctrl+a d

Session Naming and Renaming

# Create named session
screen -S database

# Inside screen: rename session
Ctrl+a :
sessionname mynewname
Enter

# Kill session from outside
screen -S mywork -X quit

# Kill all detached sessions
screen -ls | grep Detached | cut -d. -f1 | awk '{print $1}' | xargs -I {} screen -S {} -X quit

3. Window Management

Create and Navigate Windows

Ctrl+a c - Create new window
Ctrl+a A - Rename current window
Ctrl+a k - Kill current window (prompts for confirmation)
Ctrl+a \ - Kill all windows and terminate screen

Ctrl+a n - Next window
Ctrl+a p - Previous window
Ctrl+a 0-9 - Switch to window 0-9
Ctrl+a ' - Prompt for window number or name
Ctrl+a " - List all windows (interactive)

Ctrl+a Ctrl+a - Toggle between current and previous window
Ctrl+a w - Show window list in status line

Example:

# Create workflow
Ctrl+a c → Window 1 (created)
Ctrl+a A → Rename to "editor"
vim project.py
Ctrl+a c → Window 2 (created)
Ctrl+a A → Rename to "logs"
tail -f /var/log/app.log

# Navigate
Ctrl+a 0 → Switch to window 0
Ctrl+a n → Next window
Ctrl+a Ctrl+a → Toggle to previous window

4. Split Screen (Regions)

Screen supports splitting the terminal into regions (similar to tmux panes, but more limited).

Split and Navigate

Ctrl+a S - Split horizontally (create region below)
Ctrl+a | - Split vertically (create region to right) [may need -v flag]
Ctrl+a Tab - Move to next region
Ctrl+a Q - Close all regions except current
Ctrl+a X - Close current region

# After splitting, new region is empty
# Switch to it and select a window:
Ctrl+a Tab - Move to new region
Ctrl+a c - Create window in region
# or
Ctrl+a 0-9 - Display existing window in region

Example:

# Create editor + terminal layout
Ctrl+a S → Split horizontally
Ctrl+a Tab → Move to bottom region
Ctrl+a c → Create new window in region

# Result (two horizontal regions):
# 
# Window 0 
# 
# Window 1 
#

Note: Screen's split functionality is less feature-rich than tmux. Splits are not persistent across detach/reattach.

5. Copy Mode and Scrollback

Enter Copy Mode

Ctrl+a [ - Enter copy mode (scrollback)
# or
Ctrl+a Esc

# In copy mode:
Space - Start selection
Space again - End selection (copies to screen's buffer)
Ctrl+a ] - Paste from screen's buffer

Esc - Exit copy mode

h, j, k, l - Move cursor (vi-style)
0, $ - Start/end of line
w, b - Move by word
Ctrl+u, Ctrl+d - Half page up/down
Ctrl+b, Ctrl+f - Full page up/down
g, G - Top/bottom of buffer
/ - Search forward
? - Search backward
n - Next search result

Increase Scrollback Buffer

Add to ~/.screenrc:

# Default is 100 lines, increase to 10000
defscrollback 10000

6. Configuration (~/.screenrc)

Basic Configuration

Create ~/.screenrc:

# Disable startup message
startup_message off

# Increase scrollback buffer
defscrollback 10000

# Enable 256 color support
term screen-256color

# Set status line
hardstatus on
hardstatus alwayslastline
hardstatus string "%{.kW}%-w%{.bW}%t [%n]%{-}%+w %=%{..G} %H %{..Y} %Y-%m-%d %c"

# Visual bell instead of audible
vbell on
vbell_msg " Wuff ---- Wuff!! "

# Alternative caption (shows window list)
caption always "%{= kw}%-w%{= BW}%n %t%{-}%+w %-= @%H - %LD %d %LM - %c"

# Detach on hangup
autodetach on

# Enable mouse tracking (limited support)
mousetrack on

# UTF-8 support
defutf8 on

# Shell
shell -$SHELL

# Monitor window activity
defmonitor on
activity "Activity in window %n"

# Bind F1-F4 to switch windows
bindkey -k k1 select 0
bindkey -k k2 select 1
bindkey -k k3 select 2
bindkey -k k4 select 3

# Bind | for vertical split (if supported)
bind | split -v

# Bind - for horizontal split
bind - split

# Easier resize
# bind = resize =
# bind + resize +1
# bind - resize -1

Reload Configuration

# From command line
screen -X source ~/.screenrc

# Inside screen
Ctrl+a :
source ~/.screenrc
Enter

7. Advanced Features

Logging

# Inside screen: start logging window to file
Ctrl+a H

# Default log file: screenlog.0 (in current directory)

# Add to ~/.screenrc to customize:
logfile screenlog-%Y%m%d-%n.txt

Monitoring Windows

# Monitor window for activity (alerts when output appears)
Ctrl+a M

# Monitor window for silence (alerts after 30 seconds of no output)
Ctrl+a _

# Add to ~/.screenrc:
# defmonitor on # Monitor all windows by default
# activity "Window %n: activity!"

Lock Screen

# Lock screen session (requires password to unlock)
Ctrl+a x

# Will prompt for user password

Multi-User Mode (Pair Programming)

# On server, enable multiuser mode
Ctrl+a :
multiuser on
Enter

# Add user with access
Ctrl+a :
acladd username
Enter

# Other user connects:
screen -x mainuser/sessionname

# Revoke access:
Ctrl+a :
acldel username

8. SRE/DevOps Workflows

Persistent SSH Session

# SSH to remote server
ssh server01

# Start screen session
screen -S work

# Do work in multiple windows...
Ctrl+a c # new window for logs
Ctrl+a c # new window for monitoring

# Network dies or you close laptop
# Session continues running on server!

# Later: SSH back in
ssh server01

# Reattach to session
screen -r work

# Everything still running!

Serial Console Access

# Connect to serial console (common for network equipment)
screen /dev/ttyUSB0 9600

# Common baud rates: 9600, 19200, 38400, 115200

# Disconnect without closing
Ctrl+a k
y

# Or detach (keeps connection open)
Ctrl+a d

Run Long-Running Job

# Start screen
screen -S build

# Run long build
make build

# Detach
Ctrl+a d

# Log out, go home, come back tomorrow

# Reattach
screen -r build

# Build still running or completed!

Multi-Server Monitoring

# Create monitoring session
screen -S monitor

# Window 0: server01
ssh server01
top

# Window 1: server02
Ctrl+a c
ssh server02
top

# Window 2: server03
Ctrl+a c
ssh server03
htop

# Navigate between servers
Ctrl+a 0-2

9. Useful One-Liners

# Kill all detached screen sessions
screen -ls | grep Detached | cut -d. -f1 | awk '{print $1}' | xargs kill

# Create screen session, run command, detach
screen -dmS backup tar czf backup.tar.gz /data

# List all screen sessions for all users (requires root)
sudo screen -ls

# Send command to detached screen session
screen -S mywork -X stuff "ls -la\n"

# Create screen with custom window titles
screen -t "Editor" 0 vim
screen -t "Logs" 1 tail -f /var/log/app.log

# Nested screen (change command key to Ctrl+b)
screen -e ^Bb

# Start screen in background with windows
screen -dmS dev -t editor vim -t server npm start

10. Troubleshooting

Common Issues

Problem: "Cannot open your terminal '/dev/pts/0'" error

Solution:

# Fix permissions
script /dev/null
screen

# Or
sudo chmod 666 /dev/pts/0

Problem: Screen sessions not listed after reboot

Solution:

# screen sessions don't survive reboot (unlike tmux with plugins)
# Use systemd or supervisord for persistent services

Problem: Colors broken in screen

Solution:

# Add to ~/.screenrc:
term screen-256color

# Or start with:
screen -T screen-256color

Problem: Can't detach (Ctrl+a d does nothing)

Solution:

# Make sure you're typing Ctrl+a then d (not holding both)
# Or use explicit detach:
Ctrl+a :
detach
Enter

Problem: Accidentally killed screen with Ctrl+d

Solution:

# Ctrl+d exits the shell, which closes the window
# If it's the last window, screen terminates
# Prevention: use 'autodetach on' in ~/.screenrc
# Can't recover - session is gone

Problem: Screen frozen/hung

Solution:

# Flow control stopped output (Ctrl+s)
# Resume with:
Ctrl+q

# Disable flow control in ~/.screenrc:
defflow off

11. screen vs tmux

Feature	screen	tmux
Age	Since 1987	Since 2007
Default Prefix	Ctrl+a	Ctrl+b
Availability	Everywhere	Most modern systems
Split Panes	Limited, not persistent	Full support, persistent
Vertical Split	Needs flag, not all versions	Native support
Configuration	~/.screenrc	~/.tmux.conf
Status Line	Basic	Rich, customizable
Mouse Support	Limited	Full support
Plugin System	None	TPM (extensive)
Session Persistence	No (native)	Yes (with plugins)
Scripting	Basic	Advanced
Performance	Lighter	Slightly heavier
Learning Curve	Moderate	Moderate

When to use screen: - Legacy systems where tmux isn't available - Serial console access - Minimal resource usage required - Familiarity with screen from years of use

When to use tmux: - Modern systems - Need advanced pane management - Want plugin ecosystem - Prefer better defaults

12. Migration from screen to tmux

If you're used to screen but want to try tmux:

Key Binding Compatibility:

Add to ~/.tmux.conf:

# Use Ctrl+a instead of Ctrl+b (like screen)
unbind C-b
set-option -g prefix C-a
bind-key C-a send-prefix

# Last window (like screen's Ctrl+a Ctrl+a)
bind-key C-a last-window

# Kill window (like screen's Ctrl+a k)
bind-key k confirm-before -p "kill-window #W? (y/n)" kill-window

# Detach (like screen's Ctrl+a d)
bind-key d detach-client

Command Equivalents:

screen	tmux	Action
`screen -S name`	`tmux new -s name`	New session
`screen -r`	`tmux attach`	Attach
`screen -ls`	`tmux ls`	List sessions
`Ctrl+a d`	`Ctrl+b d` (or Ctrl+a with config)	Detach
`Ctrl+a c`	`Ctrl+b c`	New window
`Ctrl+a n/p`	`Ctrl+b n/p`	Next/previous window
`Ctrl+a S`	`Ctrl+b "`	Horizontal split
`Ctrl+a \|`	`Ctrl+b %`	Vertical split

13. Cheat Sheet Summary

Session Management

screen -S name - Create named session
screen -r name - Reattach to session
screen -ls - List sessions
screen -dr name - Force reattach (detach others)
Ctrl+a d - Detach from session

Windows

Ctrl+a c - Create window
Ctrl+a A - Rename window
Ctrl+a n/p - Next/previous window
Ctrl+a 0-9 - Switch to window 0-9
Ctrl+a " - List windows
Ctrl+a k - Kill window
Ctrl+a w - Window list in status

Regions (Splits)

Ctrl+a S - Horizontal split
Ctrl+a | - Vertical split
Ctrl+a Tab - Next region
Ctrl+a Q - Close all except current
Ctrl+a X - Close current region

Copy Mode

Ctrl+a [ - Enter copy mode
Space - Start/end selection
Ctrl+a ] - Paste
Esc - Exit copy mode

Misc

Ctrl+a ? - Help (show key bindings)
Ctrl+a : - Command mode
Ctrl+a H - Start/stop logging
Ctrl+a M - Monitor window activity
Ctrl+a x - Lock screen

14. Resources

Official Documentation: - https://www.gnu.org/software/screen/ - man screen - info screen

Useful Links: - GNU screen manual: https://www.gnu.org/software/screen/manual/ - screen FAQs: https://www.gnu.org/software/screen/faq.html - Arch Linux screen wiki: https://wiki.archlinux.org/title/GNU_Screen

Configuration Examples: - https://gist.github.com/joaopizani/2718397 (popular .screenrc)

Books: - "Learning the bash Shell" (includes screen chapter)

Updated: 2026-05-23 Author: Documentation Team Use Case: Terminal multiplexing, Legacy systems, Serial console, SRE

screen Quick Reference

Overview

1. Core Concepts

Session Management

2. Session Management

Create and Attach Sessions

Session Naming and Renaming

3. Window Management

Create and Navigate Windows

4. Split Screen (Regions)

Split and Navigate

5. Copy Mode and Scrollback

Enter Copy Mode

Copy Mode Navigation

Increase Scrollback Buffer

6. Configuration (~/.screenrc)

Basic Configuration

Reload Configuration

7. Advanced Features

Logging

Monitoring Windows

Lock Screen

Multi-User Mode (Pair Programming)

8. SRE/DevOps Workflows

Persistent SSH Session

Serial Console Access

Run Long-Running Job

Multi-Server Monitoring

9. Useful One-Liners

10. Troubleshooting

Common Issues

11. screen vs tmux

12. Migration from screen to tmux

13. Cheat Sheet Summary

Session Management

Windows

Regions (Splits)

Copy Mode

Misc

14. Resources