El famoso terminal multiplexer (sorry not sorry but screen is a piece of shit).
Sync panels can be quite usefull to do the same tasks on a different set of servers.
[...] unbind S bind S set-windows-option synchronize-panes [...]
Typical use case can be updating let's say 3 Debian servers.
- start tmux
- split in 3, use ssh to connect to the targets1.
bind prefix + Sto activate sync2
apt update && apt upgrade
- And voilà !
a dedicated session can be used to automate stuff, more on that later...
by default, Ctrl + b