Tmux For Session Sharing And Process Reattachment

Getting Started with Tmux

Installing and launching tmux

Tmux is a terminal multiplexer that allows multiple terminal sessions to be accessed simultaneously in a single window. To get started with tmux, first install it on your system with your package manager of choice.

On Linux:

$ sudo apt install tmux #Ubuntu/Debian
$ sudo yum install tmux #RHEL/CentOS
$ sudo dnf install tmux #Fedora

Once installed, simply type tmux in your terminal to start a new tmux session. You will notice your terminal prompt is now prefixed with tmux, indicating you are inside a tmux session.

Understanding tmux concepts – sessions, windows, panes

Tmux provides several abstractions for managing multiple processes:

Sessions – An overarching tmux session that can contain multiple windows.
Windows – A single viewport onto one or more panes. You can have multiple windows in a session.
Panes – A single terminal instance within a window. Panes can run shell prompts, text editors, etc.

Conceptually, a session is a collection of windows, while each window divides itself into one or more panes. You can easily create, delete, rearrange, and navigate these components.

Basic tmux commands – new session, split pane, switch pane

Here are some basic tmux commands to get started:

# Start new session
tmux new -s mysession

# Split pane horizontally 
Ctrl+b " 

# Split pane vertically
Ctrl+b %

# Switch to next pane
Ctrl+b o 

# Switch to session "mysession" 
tmux attach -t mysession

# Detach from session
Ctrl+b d

This allows you to start making use of tmux’s session, window, and pane abstractions.

Sharing Tmux Sessions

Enabling other users to attach

By default, tmux sessions can only be accessed by the user who started them. To enable other users to attach:

# Allow other users to read/write
tmux set -t mysession acl-add user123 -w

# Allow other users read-only access
tmux set -t mysession acl-add user456 -r

Now user123 can attach to “mysession” with full access, while user456 has read-only access.

Detaching and reattaching to sessions

To detach from a tmux session:

Ctrl+b d

This keeps the tmux session running in the background.

To reattach later:

  
tmux attach -t mysession

This lets you resume right where you left off in “mysession”.

Read-only access for collaboration

You can grant other users read-only access to a session for collaborating:

tmux set -t mysession acl-add user456 -r

Now when user456 attaches to “mysession”, they will not be able to send keystrokes/commands. This allows them to observe without disrupting the session.

Great for pair programming, mentoring, etc!

Tmux Persistence

Keeping sessions running after detach

Tmux keeps sessions persistent by default when detached. This preserves all programs running within.

To explicitly configure this:

# In ~/.tmux.conf
set -g detach-on-destroy off

Now tmux sessions will continue running in the background when detached.

Reattaching to previous sessions

If tmux is closed improperly or crashes, you can resume prior sessions with:

tmux attach -t mysession

This reattaches to the persistent “mysession” in the background.

Session names for easy reattachment

Use descriptive session names like “dev” or “docs” for convenience:

tmux new -s dev
tmux new -s docs

You can now easily resume either session via name:

tmux attach -t dev
tmux attach -t docs

Advanced Tmux Usage

Customizing status bar and colors

Tmux offers extensive customization via ~/.tmux.conf. For example, to configure the status bar:

# In ~/.tmux.conf

# Status bar colors
set -g status-bg black
set -g status-fg white

# Left aligned info
set -g status-left "#S [#I:#P]"

# Window numbering
set -g status-right "#(tmux-mem-cpu-load)#W"

# Activity monitoring
setw -g monitor-activity on
set -g visual-activity on

There are many color, style, and information options available for the status bar.

Scripting and automation with tmux

Commands can be run when certain tmux conditions occur by binding scripts to hooks:

# Runs on session create
set -g status-right "#(tmux-mem-cpu-load)#W"

# Run script when window closed
set-hook -g session-destroy-hook '/home/user123/tmux-cleanup.sh' 

# Bind key to script 
bind R run '~/reload-config.sh'

This allows extensive tmux automation via shell scripts.

Integrating with shell and text editors

Tmux works well with other terminals like vim/neovim. For example:

# Vim/Tmux integration
set -g status-right "#(tmux-mem-cpu-load)#W"

# Mouse support in vim
set -g mouse on

# Easy switching between vim and tmux panes
bind h select-pane -L 
bind j select-pane -D
bind k select-pane -U
bind l select-pane -R

Similar integrations are available for shells like zsh too.

Tmux Tips and Tricks

Scrollback, copy mode, and search

Tmux allows scrolling through previous terminal output via copy mode:

# Enter copy mode
Ctrl+b [ 

# Scroll up/down with Vi keys
Up, Down 

# Search output
Ctrl+f

# Copy highlighted text
Ctrl+Spacebar

This lets you revisit old content printed in tmux.

Layouts and pane arrangements

Tmux offers many preset pane layouts:

# Split 4 panes evenly 
Ctrl+b Meta+1

# 2 panes top and bottom
Ctrl+b Meta+2 

# 2 panes side by side
Ctrl+b Meta+3

# Cycle layouts
Ctrl+b Spacebar

You can create custom layouts as well in ~/.tmux.conf for added flexibility.

Debugging and troubleshooting FAQs

Some tips for resolving issues:

Use tmux info to diagnose session/server issues
Check ~/.tmux.conf for incorrect syntax or bindings
Disable plugins and customizations to isolate problems
See status bar for warnings about unsupported features
Search logs at /var/log/tmux.log for error messages

The tmux mailing list at [email protected] is also a great resource!