The prefix key is an essential part of tmux, by default all of tmux's
key-bindings sit behind a prefix. This prefix is very similar to vim's leader
key. It is common for folks to change the default
C-b (control b) to
if they are a vim user something to match their vim leader key.
set -g prefix C-Space bind Space send-prefix
A few of the essential default key-bindings.
% vertical split " horizontal split d detach up select up one pane down select down one pane right select right one pane left select left one pane t clock o swap panes c create window n next window p previous window
A more complete list of key-bindings can be found in this gist https://gist.github.com/mzmonsour/8791835.
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Also check out this long form post for more about how I use tmux.