If you try to execute a command inside the docker using the Jenkins or jus try to use the -it
option in the docker run
command, you will get the following error:
the input device is not a TTY
How to fix the error?
The fix is pretty simple, all you need to do is to remove the -it
options from the docker run
command. If you want to know why is that, you can continue reading the following section.
Why do a get this error?
The docker run/exec -i
command will connect the STDIN (Standard input) of the command inside the container to the STDIN of the docker run/exec
itself.
Try running something like this: docker run -i ubuntu cat
You will notice that the container will not exit until you send CTRL+D
because the main process cat
is for input from the infinite stream that is the terminal input of the docker run
If you try something like this: echo "hello" | docker run -i ubuntu cat
(notice the pipe operator). It will print hello
and exit right after because docker noticed that the cat
command terminated, thus docker terminated the container.
If you change the -i
option to -t
option, the command will look like this: docker run -t ubuntu cat
. It will give you an empty line, because while the cat is connected to the input, the input is not connected your input (as mentioned before). If you get your shell back by pressing CTRL + C
, and then list all running containers, you will notice that the container is still running, because the cat
is still waiting for input.
Now, for -it
together. This tells cat that its input is a terminal and in the same time connect this terminal to the input of docker run
which is a terminal. docker run/exec
will make sure that its own input is in fact a tty before passing it to cat
. This is why you will get a input device is not a TTY
if you try echo "hello" | docker run -it alpine cat
because in this case, the input of docker run
itself is the pipe from the previous echo and not the terminal where docker run
is executed.
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