docker exec -it returns "cannot enable tty mode on non tty input"

Question

docker exec -it command returns following error "cannot enable tty mode on non tty input"

level="fatal" msg="cannot enable tty mode on non tty input" 

I am running docker(1.4.1) on centos box 6.6. I am trying to execute the following command docker exec -it containerName /bin/bash but I am getting following error

level="fatal" msg="cannot enable tty mode on non tty input" 

Answer 1

Running docker exec -i instead of docker exec -it fixed my issue. Indeed, my script was launched by CRONTAB which isn't a terminal.

As a reminder:

Usage: docker exec [OPTIONS] CONTAINER COMMAND [ARG...]

Run a command in a running container

  -i, --interactive=false    Keep STDIN open even if not attached  
  -t, --tty=false            Allocate a pseudo-TTY