What exactly does this option do? I've been reading a lot on TTY and am still confused. I played around with not having the -t
and just -i
and it seems like programs that expect user input throw an error without the -t
. Why is it important for pseudo-TTY to be enabled?
The -t
option goes to how Unix/Linux handles terminal access. In the past, a terminal was a hardline connection, later a modem based connection. These had physical device drivers (they were real pieces of equipment). Once generalized networks came into use, a pseudo-terminal driver was developed. This is because it creates a separation between understanding what terminal capabilities can be used without the need to write it into your program directly (read man pages on stty
, curses
).
So, with that as background, run a container with no options and by default you have a stdout stream (so docker run | <cmd>
works); run with -i
, and you get stdin stream added (so <cmd> | docker run -i
works); use -t
, usually in the combination -it
and you have a terminal driver added, which if you are interacting with the process is likely what you want. It basically makes the container start look like a terminal connection session.