I am reading the spec of the run command and see the following:
-i : Keep STDIN open even if not attached
and
-a=[] : Attach to
STDIN,STDOUTand/orSTDERR
and
You can specify to which of the three standard streams (STDIN, STDOUT, STDERR) you’d like to connect
But I lack of understanding: what does it mean to "connect a container to a standard stream?" Can somebody explain? What does for example the -i parameter do?
Well, STDIN (Standard Input), STDOUT (Standard Output), STDERR (Standard Error) are three standard stream.
Normally, STDIN means keyboard, STDOUT and STDERR mean the direct screen display.
So, if you want to give your container some input from keyboard, you need to connect it to the STDIN. And if you want your container print the result on the screen, you may need to connect it to STDOUT and STDERR.
Otherwise, your container can run in the background. Input may come from, say, network and output may be stored in a log file.
if you want to execute any command on running container tty you need to attach a standard stream for input, output or error (STDIN, STDOUT, STDERR).
So you can keep the tty intractive using -i command even if stream is not attached.
or can directly execute attach using -it {running container id} /bin/bash
can keep the tty intractive .. if stream is not attached What can I do, when the tty is interactive and no stream is attached? What changes when tty is interactive and the stream is attached ? tty interactive means - I can pass commands to container via exec, and it will be redirected to the container tty?