I am confused about these three commands, I don't know the difference among them. Sorry, I am new to docker.
I can not see the difference from the result.Could anybody tell me the difference?
docker run -it IMAGE_NAME /bin/bash
docker run -i IMAGE_NAME /bin/bash
docker run -i IMAGE_NAME
From the docker documentation
-t : Allocate a pseudo-tty
-i : Keep STDIN open even if not attached
For interactive processes (like a shell), you must use -i -t together in order to allocate a tty for the container process.
docker run -i imagename /bin/bash
This will attach a shell to the container. You can run any shell command on the shell.
docker run -i imagename
This will dump the stdout on the terminal. Similar to docker run but with ability to take input from pipe.
Docker run command has some parameters to run command in Detached or Foreground mode.
-i and -t falls under Foreground mode.
-i : Keep STDIN open even if not attached
-t : Allocate a pseudo-tty
In case of -i whenever you run docker container command passed to it will be fired. in your case "/bin/bash"
Note from Doc
For interactive processes (like a shell), you must use -i -t together
in order to allocate a tty for the container process. -i -t is often
written -it as you’ll see in later examples. Specifying -t is
forbidden when the client is receiving its standard input from a pipe,
as in:
More Detail Here
docker run -it IMAGE_NAME /bin/bash --> you will be able to enter into container if you use -i(interactive) option (which is for executing any commands in the container) and -t(tty) which gives you the terminal to enter any command, /bin/bash is the type of linux shell (eg. sh,ksh,bash etc.)
Related
Why when i run the command
docker run ubuntu
without option '-it' is not possible to interact with the created container even when running command start with the -a -i options
docker start -a -i CONTAINER_ID
or when i run
docker start CONTAINER_ID
simply the container has the status "Exit (0) 4 seconds ago"
But when i run
docker run -it ubuntu
i can use bash shell of ubuntu using 'docker start -a -i'
When you run docker run without -it it's still running the container but you've not given it a command, so it finishes and exits.
If you try:
docker run ubuntu /bin/bash -c "echo 'hello'";
It'll run ubunu, then the command, and then finish because there is no reason for it to be kept alive afterwards.
-i is saying keep it alive and work within in the terminal (allow it to be interactive), but if you type exit, you're done and the container stops.
-t is showing the terminal of within the docker container (see: What are pseudo terminals (pty/tty)?)
-it allows you to see the terminal in the docker instance and interact with it.
Additionally you can use -d to run it in the background and then get to it afterwards.
Ex:
docker run -it -d --name mydocker ubuntu;
docker exec -it mydocker /bin/bash;
TLDR is -it allows you connect a terminal to interactively connect to the container.
If you run docker run --help, you can find the details about docker run options.
$ docker run --help
Usage: docker run [OPTIONS] IMAGE [COMMAND] [ARG...]
Run a command in a new container
Options:
...
-i, --interactive Keep STDIN open even if not attached
...
-t, --tty Allocate a pseudo-TTY
Build an image based on the Dockerfile:
docker image build .
The result of above is
docker run --rm -ti <IMAGE_ID>
--rm : If instead you’d like Docker to automatically clean up the container and remove the file system when the container exits, you can add the --rm flag src : https://docs.docker.com/engine/reference/run/
What does the -ti argument achieve ?
-it is shorthand for -i -t
By Docker Run docs
-i Keep STDIN open even if not attached
-t Allocate a pseudo-tty
Which means, t for open a shell terminal (telewriter) and i listen to standard input.
It's basically just -i and -t which is mostly written as -it.
-i:
Keep STDIN open even if not attached
-t:
Allocate a pseudo-TTY
See: https://docs.docker.com/engine/reference/commandline/exec/
It's most common way of using Docker containers, so you can actually use them to execute some of your commands.
i stands for interactive and it's accepts and responds on your input using STDIN.
t is for you to have terminal - it's combined with i so you can actually put your input there.
Check more here and here.
I am newbie with docker, I was reading few of things and I realized some one using -it and someone -ti.
So I want to know what is the difference between docker exec -ti my_container and docker exec -it my_container.
There's no difference. -it is just a shorthand way of specifying the two flags -i and -t, as explained in the documentation:
Single character command line options can be combined, so rather than typing docker run -i -t --name test busybox sh, you can write docker run -it --name test busybox sh.
The -t flag assigns a pseudo-tty or terminal inside our new container and the -i flag allows us to make an interactive connection by grabbing the standard in (STDIN) of the container.
Since these boolean flags can be specified in any order, -ti is equivalent to -it.
This is a very common feature of Unix-y command-line tools.
I would like to know why docker -i -t -d centos /bin/bash makes a container run in background while docker -d centos /bin/bash make a container go to exit state
Hey guys, I am trying to understand why -i -t makes a container stay in active state. I would have thought that -d would have been enough in above scenario.
$ docker run -d --name mycentos3 centos
0bebdb11f3796bf5ac1ee9b0f132c3b3a4fcc2390f77aa971e6700d025025ebb
docker run -i -t -d --name mycentos4 centos
2be599d7310677c53c6f1dd1b5c70106f4c33f3193aad466ca34f0855173e559
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
2be599d73106 centos "/bin/bash" Less than a second ago Up 1 second mycentos4
Bash is an interactive prompt. It consumes input from STDIN.
-i is necessary in order for Docker to keep a STDIN open. Without it: bash would reach the end of input and terminate.
-d is not related to your problem.
-t is not responsible for bash's exiting, but it's good to use -t for interactive prompts like bash, so that Docker provides a pseudo-TTY into which bash can write prompts (e.g. your PS1) and control sequences (e.g. colour).
I was doing some complex stuff with docker, but as turn out I don't know what -it flag means.
Recently I've come across on some example of docker run command which has confused me a little.
docker run -itd ubuntu:xenial /bin/bash
My question is what is sense to write -it flag here, if container during instantiation run bin/bash
In documentation we have an example
docker run --name test -it debian
with explanation
The -it instructs Docker to allocate a pseudo-TTY connected to the
container’s stdin; creating an interactive bash shell in the
container.
and explanation for -t flag from help page
-t, --tty Allocate a pseudo-TTY
if I delete -it flag during
docker run -d ubuntu:xenial /bin/bash
my newly created container doesn't live so much
in docker ps -a
it is designated as exited
Sorry, if my question quite stupid, I can't find explanation on the Internet (I have significant misunderstanding of that point).
-it is short for --interactive + --tty. When you docker run with this command it takes you straight inside the container.
-d is short for --detach, which means you just run the container and then detach from it. Essentially, you run container in the background.
Edit: So if you run the Docker container with -itd, it runs both the -it options and detaches you from the container. As a result, your container will still be running in the background even without any default app to run.
docker run -it ubuntu:xenial /bin/bash starts the container in the interactive mode (hence -it flag) that allows you to interact with /bin/bash of the container. That means now you will have bash session inside the container, so you can ls, mkdir, or do any bash command inside the container.
The key here is the word "interactive". If you omit the flag, the container still executes /bin/bash but exits immediately. With the flag, the container executes /bin/bash then patiently waits for your input.
Normal execution without any flags:
[ec2-user#ip-172-31-109-14 ~]$ sudo docker exec 69e937450dab ls
bin
boot
dev
docker-entrypoint.d
docker-entrypoint.sh
etc
If your command needs an input like cat, you can try:
[ec2-user#ip-172-31-109-14 ~]$ echo test | sudo docker exec 69e937450dab cat
Nothing will show, because there is no input stream going to the docker container. This can be achieved with the -i flag.
[ec2-user#ip-172-31-109-14 ~]$ echo test | sudo docker exec -i 69e937450dab cat
test
Now, let us suppose, you want the bash to start as process:
sudo docker exec 69e937450dab bash
You will see nothing, because the process started in the container. Adding the flag will do the deal:
[ec2-user#ip-172-31-109-14 ~]$ sudo docker exec -t 69e937450dab bash
root#69e937450dab:/#
But this does not really help, because we need an input stream, which takes our commands and can be received by the bash. Therefore, we need to combine the two:
[ec2-user#ip-172-31-109-14 ~]$ sudo docker exec -i -t 69e937450dab bash
root#69e937450dab:/# ls
bin boot dev docker-entrypoint.d docker-entrypoint.sh etc hi home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root#69e937450dab:/#
small recap:
-t for attaching the bash process to our terminal
-i for being able to send inputs via STDIN for example with the keyboard to the bash in the container
Without -i can be used for commands, that don't need inputs. Without -t and bash can be used, when you dont want to attach the docker containers process to your shell.