I'm a little confused by some docker flags, and more particularly by the "i", "t" and "it" flags.

First, is "docker run -it" equivalent to "docker run -i -t" ?

Second, what does "Allocate a pseudo-TTY" exactly means (it is the documentation of the "-t" flag) ?

I've conducted a couple of tests with an image (called hello-world) having

CMD ["echo", "Hello docker world !!!"]

or

ENTRYPOINT  ["echo", "Hello docker world !!!"]

The following commands :

• docker run -i -t hello-world
• docker run -i hello-world
• docker run -t hello-world
• docker run -it hello-world
• docker run hello-world

all resulted in the display of the text "Hello world". I would expect at least the last one to not display anything...

CodePudding user response：

Those are called flags and a flag can either be combined or separated, either in short (-) or long format (--). So:

docker run --interactive --tty hello-world

docker run --interactive -t hello-world

docker run -i --tty hello-world

docker run -i -t hello-world

docker run -it hello-world

are all the same.

As to how -i and -t works, refer to this

CodePudding user response：

In this above simple example it will work the same.

In the last example container will print "Hello..." and exit in contrary to when you start interactive mode: https://phoenixnap.com/kb/docker-run-command-with-examples (-i -t -it will work the same)

For the difference cmd and entrypoint refer here: What is the difference between CMD and ENTRYPOINT in a Dockerfile?