tmux

Identity

Property	Value
Binary	`tmux`
Config	`~/.tmux.conf` or `/etc/tmux.conf`
Logs	No persistent logs — output to terminal
Type	CLI tool
Install	`apt install tmux` / `dnf install tmux`

Task	Command
New named session	`tmux new-session -s mysession`
Attach to named session	`tmux attach-session -t mysession`
Attach or create if absent	`tmux new-session -A -s mysession`
List all sessions	`tmux list-sessions`
Detach from session	prefix + `d`
New window	prefix + `c`
Next / previous window	prefix + `n` / `p`
Switch to window by number	prefix + `0`-`9`
Split pane horizontal (side by side)	prefix + `%`
Split pane vertical (top/bottom)	prefix + `"`
Navigate between panes	prefix + arrow keys
Resize pane	prefix + Ctrl+arrow (hold Ctrl, tap arrow)
Kill current pane	prefix + `x`
Kill current window	prefix + `&`
Kill a session	`tmux kill-session -t mysession`
Enter copy mode	prefix + `[`
Rename current window	prefix + `,`
Rename current session	prefix + `$`
Send same command to all panes	`tmux set-option -g synchronize-panes on`
Run command in a new detached session	`tmux new-session -d -s work 'top'`

Symptom	Cause	Fix
`tmux attach` says "no sessions"	No running sessions	Start one: `tmux new-session -s main`
Ctrl+b conflicts with readline	Default prefix is Ctrl+b, same as readline "back char"	Remap in `~/.tmux.conf`: `set -g prefix C-a` + `bind C-a send-prefix`
Copy doesn't reach system clipboard	tmux copy mode uses internal buffer, not X clipboard	Install `xclip` and add: `bind -T copy-mode-vi y send -X copy-pipe 'xclip -sel clip'`
Mouse mode not working	Not enabled by default	Add to `~/.tmux.conf`: `set -g mouse on`
Nested tmux: inner prefix swallowed	Outer tmux intercepts the prefix	Send prefix to inner: press prefix twice (`Ctrl+b Ctrl+b`)
Colours look wrong in tmux	Terminal `TERM` not set to 256color	Add to `~/.tmux.conf`: `set -g default-terminal "screen-256color"`
Session not persisting after SSH disconnect	Session was foreground process, not tmux	Always start work in a named tmux session before running long jobs

Default prefix Ctrl+b conflicts with readline: Readline uses Ctrl+b to move the cursor back one character. Most users remap the tmux prefix to Ctrl+a (matching GNU screen's default) in ~/.tmux.conf.
Copy-paste requires extra configuration: tmux copy mode fills an internal buffer. Getting content into the system clipboard requires xclip, xsel, or OSC 52 passthrough, plus config to wire them together. This is not set up by default.
Nested tmux needs double-prefix: When ssh-ing into a remote host that also runs tmux, the local tmux intercepts the prefix. Send a prefix to the inner session with two prefix presses: C-b C-b for the inner window, C-b C-b C-b to send a literal C-b.
tmux new vs tmux new-session: Both work interactively, but scripts should use new-session for clarity. tmux new -A -s name is the idiomatic "attach if exists, create if not" pattern.
Mouse mode must be enabled explicitly: set -g mouse on enables click-to-focus, scrolling, and pane resizing via mouse. Without it, the mouse has no effect and scrolling uses the terminal emulator's scroll buffer instead of tmux's.