I have a docker service/image I'm using which restarts as soon as starts.
I'm unable to fix the issue by getting into the container using
docker exec -it CONTAIER_NAME
since it restarts/terminates as soon as it boots.
Is there anyway I can pause it directly? I can't rebuild the image as I don't have access to the internet on the server. (Yes I'm sure the rebuild or build--no-cache will fix the issue)
The issue should be easily fixable if I modify permissions for a certain folder, but I'm not sure how to do this inside the container when I can't access it. The image doesn't have a docker file and is used directly from the docker hub.
If we do not get any information from the container's logs, we have the option to start the process "manually". For this, we start the container with an interactive terminal (-it, -i to keep STDIN open, -t to open a pseudo-TTY) and override the entrypoint to be a shell, e.g. bash. For good measure, we want the container to be removed when it terminates (i.e. when we exit the termainal, --rm):
docker run ... -it --rm --entrypoint /bin/bash
Once inside the container, we can start the process that would have normally started through the entrypoint from the container's terminal and extract error information from here.
faced with issue : when i am trying to run container :
docker run -t -p 3000:3000 --name container-dev-local image-dev-local
i am getting pretty much colored output with my logs :
But :
how can i exit without stopping container? Ctrl+P + Ctrl+Q don't work, it exiting and stop container
Update:
found the way to start without attaching by adding -d param :
docker run -d -p //other params
so now, after run - it starts in detached state, but colored logs dissapearing when i tried to attach
docker attach --sig-proxy=false container-dev-local
But after attaching i still can't exit from it without stopping process, CTRL+C, CTRL+P+Q does not work - it suspending process.
And how can i return back colorized logs? Have no ideas
My pre-requisites are : Windows 10, .net core inside of .nix container, visual studio 2019 and powershell terminal.
Found the solution!
First, you need to apply to docker run "-dti" flag, it enabling tty + detached mode (see docs)
It allows you to run container and trying to attach to it by
docker attach --sig-proxy=false container-dev-local
So now, you should see colored logs as -ti is also applied during run command.
How to exit without termination?
First, you can try Ctrl+Z+C (Z and C should be pressed in time of pressing Ctrl) command. It will stop your outer task and your terminal will ask you "Stop job?(y/n)" - then type "n" and ... should work :) You will be detached, container will continue work.
Second, we can override "detached keys" by adding --detach-keys :
docker attach --sig-proxy=false --detach-keys="ctrl-c" container-dev-local
And then, just try to simply use Ctrl+C, the same result will be achieved.
About CTRL+Z you can get some info here : What's different between Ctrl+Z and Ctrl+C in Unix command line
If I use docker exec to fire up a shell,
docker exec -ti <CONTAINER> /bin/bash
I could use Ctrl+p Ctrl+q to detach this shell process. Then this shell is still running inside the container, but how can I reattach to that one particular shell (the one started by docker exec, not docker run)?
Sadly, this is not possible yet; see this issue on GitHub. I've also wanted this functionality, but at the moment it seems like there's no direct way to do this.
A workaround has been proposed, to take care of the case where you're accessing a box via ssh and running docker exec on the remote box (or, for the case where your terminal emulator is unstable and may crash on you): Always run your docker exec commands inside screen or tmux. If you do this, whenever you get detached from the screen/tmux session, you can re-attach to it later and still have your docker exec commands accessible. (this is a bit different than what was suggested by #vodolaz095, since it involves running screen or tmux outside the container, making it suitable for use with containers that don't run screen/tmux as their main process)
docker exec is specifically for running new things in an already started container, be it a shell or some other process.
docker attach is for attaching to a running process, so you can use only one instance of shell.
Run you container(process)
docker run -tid --name <CONTAINER> <IMAGE>:<TAG> bin/bash
Then
docker attach <CONTAINER>
To detach Ctrl+p + Ctrl+q
On this way you can attach and detach multiple times with only one instance of shell
I have a docker image with all the necessary tools and environment properly set up. However, I am having a hard time running it in the background.
Seems like there are two approaches:
(1) can run the box as daemon and I can attach to it whenever I want to use the box. However, the container exit with code zero right after I run it as daemon.
$:~/docker/docker_scrapy$ sudo docker run -ti -v ~/docker/docker_scrapy/myvolume:/var/myvolume 3fb9894af1d9 /bin/bash
root#3fc39116a586:/# python -c 'from bs4 import BeautifulSoup'
root#3fc39116a586:/# cd /var/myvolume/
root#3fc39116a586:/var/myvolume#
$:~/docker/docker_scrapy$ sudo docker run -d -v ~/docker/docker_scrapy/myvolume:/var/myvolume 3fb9894af1d9
c5fab6e6ac02a579e3371aa641b18ca67feb93a9f4f4934b6d083157182fe4e1
$:~/docker/docker_scrapy$ sudo docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
Clearly, I can start the box in the interactive mode, but when I try to run it as a daemon, it will exit with code 0 right after I started. And I can not attach to it because I need to start it. Does that mean you can not run a image in the daemon mode if it is idle?
(2 )Or setting it up as a SSH server, and I can ssh in and do the work whenever I want. Like Vagrant up/ssh..
In summary:
(1) What did I do wrong with the detach/attach?
(2) Which is the proper way to have a run docker in the background? daemon/ssh
If you give it another command to run after starting the service that waits for input then the container will keep running until you attach and exit that command. I usually leave a shell running after the service starts so I can debug things. here's a simple example:
First let's create a service that runs in the background
arthur#a:~$ docker run -ti ubuntu bash
root#5dc7f330b947:/# cat <<'EOF' >start-service.sh
> while true
> do
> echo service is running >> service.log
> sleep 10
> done
> EOF
root#5dc7f330b947:/# chmod +x start-service.sh
root#5dc7f330b947:/# exit
arthur#a:~$ docker ps -l
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
5dc7f330b947 ubuntu:12.04 bash 50 seconds ago Exited (0) 3 seconds ago jolly_nobel
arthur#a:~$ docker commit 5dc7f330b947 service/example
4c37b69b129287d79a6fe3916e4293f935194966b1de49d125f1cf8d6ab14f6f
then we can start it (i background it with a & here. in your example the & would not be required). Note it's fine to use both the interactive and detach options.
arthur#a:~$ docker run -ti -d service/example bash -c "./start-service.sh & bash"
b35a5397ea2d29b4085d93ef32270379b09e49118380b0376309bca74fd719d0
arthur#a:~$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
b35a5397ea2d service/example:latest bash -c './start-ser 7 seconds ago Up 7 seconds cranky_wright
later we can attach and check on the service by looking in it's log file:
arthur#a:~$ docker attach b35a5397ea2d
root#b35a5397ea2d:/# cat service.log
service is running
service is running
service is running
root#b35a5397ea2d:/#
I don't recommend running sshd inside the container because it leaves an option for attackers that isn't strictly useful for me.
A lots of questions in there. I would firstly suggest you go through the docker tutorial to grasp some of the underlying concepts. That said...
That Dockerfile will never run in the background, that's not how docker works. There is no cmd, no entrypoint, nothing to run.
Docker by default runs one task, when that returns the container stops. So if all you wanted was a sshd you would run that as your CMD in non daemon mode. (sshd -D)
There are ways to run daemonized apps though:
Using supervisord, as documented on the docker site.
Another alternative is phusion/baseimage.
Phusion/baseimage provides ssh access, but honestly to do what I need in containers I find nsenter easier to use. Especially when paired with the phusion docker-bash tool.
Notice: this answer promotes a tool I've written.
First of all, conceptually running multiple processes in one container is not the right approach (https://docs.docker.com/articles/dockerfile_best-practices/). A more favorable solution is one that involves multiple containers each running their own process/service. Linking them together would result in a coherent application.
I've created a containerized SSH server that you can 'stick' to any running container. This way you can create compositions with every container, without that container even knowing about ssh. The only requirement is that the container has bash.
The following example would start an SSH server attached to a container with name 'sshd-web-server1'.
docker run -ti --name sshd-web-server1 -e CONTAINER=web-server1 -p 2222:22 \
-v /var/run/docker.sock:/var/run/docker.sock -v $(which docker):/usr/bin/docker \
jeroenpeeters/docker-ssh
You connect to the SSH server with your ssh client of choice, just as you normally would.
Be adviced: Docker-SSH is currently still under development, but it does work! Please let me know what you think
For more pointers and documentation see: https://github.com/jeroenpeeters/docker-ssh
In Docker 1.1.2 (latest), what's the correct way to detach from a container without stopping it?
So for example, if I try:
docker run -i -t foo /bin/bash or
docker attach foo (for already running container)
both of which get me to a terminal in the container, how do I exit the container's terminal without stopping it?
exit and CTR+C both stop the container.
Type Ctrl+p then Ctrl+q. It will help you to turn interactive mode to daemon mode.
See https://docs.docker.com/engine/reference/commandline/cli/#default-key-sequence-to-detach-from-containers:
Once attached to a container, users detach from it and leave it running using the using CTRL-p CTRL-q key sequence. This detach key sequence is customizable using the detachKeys property. [...]
Update: As mentioned in below answers Ctrl+p, Ctrl+q will now turn interactive mode into daemon mode.
Well Ctrl+C (or Ctrl+\) should detach you from the container but it will kill the container because your main process is a bash.
A little lesson about docker.
The container is not a real full functional OS. When you run a container the process you launch take the PID 1 and assume init power. So when that process is terminated the daemon stop the container until a new process is launched (via docker start) (More explanation on the matter http://phusion.github.io/baseimage-docker/#intro)
If you want a container that run in detached mode all the time, i suggest you use
docker run -d foo
With an ssh server on the container. (easiest way is to follow the dockerizing openssh tutorial https://docs.docker.com/engine/examples/running_ssh_service/)
Or you can just relaunch your container via
docker start foo
(it will be detached by default)
I dug into this and all the answers above are partially right. It all depends on how the container is launched. It comes down to the following when the container was launched:
was a TTY allocated (-t)
was stdin left open (-i)
^P^Q does work, BUT only when -t and -i is used to launch the container:
[berto#g6]$ docker run -ti -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
b26e39632351192a9a1a00ea0c2f3e10729b6d3e22f8e0676d6519e15c08b518
[berto#g6]$ docker attach test
# here I typed ^P^Q
read escape sequence
# i'm back to my prompt
[berto#g6]$ docker kill test; docker rm -v test
test
test
ctrl+c does work, BUT only when -t (without -i) is used to launch the container:
[berto#g6]$ docker run -t -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
018a228c96d6bf2e73cccaefcf656b02753905b9a859f32e60bdf343bcbe834d
[berto#g6]$ docker attach test
^C
[berto#g6]$
The third way to detach
There is a way to detach without killing the container though; you need another shell. In summary, running this in another shell detached and left the container running pkill -9 -f 'docker.*attach':
[berto#g6]$ docker run -d --name test python:3.6 /bin/bash -c 'while [ 1 ]; do sleep 30; done;'
b26e39632351192a9a1a00ea0c2f3e10729b6d3e22f8e0676d6519e15c08b518
[berto#g6]$ docker attach test
# here I typed ^P^Q and doesn't work
^P
# ctrl+c doesn't work either
^C
# can't background either
^Z
# go to another shell and run the `pkill` command above
# i'm back to my prompt
[berto#g6]$
Why? Because you're killing the process that connected you to the container, not the container itself.
If you do "docker attach "container id" you get into the container.
To exit from the container without stopping the container you need to enter Ctrl+P+Q
I consider Ashwin's answer to be the most correct, my old answer is below.
I'd like to add another option here which is to run the container as follows
docker run -dti foo bash
You can then enter the container and run bash with
docker exec -ti ID_of_foo bash
No need to install sshd :)
Try CTRL+P,CTRL+Q to turn interactive mode to daemon.
If this does not work and you attached through docker attach, you can detach by killing the docker attach process.
Better way is to use sig-proxy parameter to avoid passing the CTRL+C to your container :
docker attach --sig-proxy=false [container-name]
Same option is available for docker run command.
The default way to detach from an interactive container is Ctrl+P Ctrl+Q, but you can override it when running a new container or attaching to existing container using the --detach-keys flag.
You can use the --detach-keys option when you run docker attach to override the default CTRL+P, CTRL + Q sequence (that doesn't always work).
For example, when you run docker attach --detach-keys="ctrl-a" test and you press CTRL+A you will exit the container, without killing it.
Other examples:
docker attach --detach-keys="ctrl-a,x" test - press CTRL+A and then X to exit
docker attach --detach-keys="a,b,c" test - press A, then B, then C to exit
Extract from the official documentation:
If you want, you can configure an override the Docker key sequence for detach. This is useful if the Docker default sequence conflicts with key sequence you use for other applications. There are two ways to define your own detach key sequence, as a per-container override or as a configuration property on your entire configuration.
To override the sequence for an individual container, use the --detach-keys="<sequence>" flag with the docker attach command. The format of the <sequence> is either a letter [a-Z], or the ctrl- combined with any of the following:
a-z (a single lowercase alpha character )
# (at sign)
[ (left bracket)
\ (two backward slashes)
_ (underscore)
^ (caret)
These a, ctrl-a, X, or ctrl-\\ values are all examples of valid key sequences. To configure a different configuration default key sequence for all containers, see Configuration file section.
Note: This works since docker version 1.10+ (at the time of this answer, the current version is 18.03)
If you just want see the output of the process running from within the container, you can do a simple docker container logs -f <container id>.
The -f flag makes it so that the output of the container is followed and updated in real-time. Very useful for debugging or monitoring.
In Docker container atleast one process must be run, then only the container will be running the docker image(ubuntu,httd..etc, whatever it is) at background without exiting
For example in ubuntu docker image ,
To create a new container with detach mode (running background atleast on process),
docker run -d -i -t f63181f19b2f /bin/bash
it will create a new contain for this image(ubuntu) id f63181f19b2f . The container will run in the detached mode (running in background) at that time a small process tty bash shell will be running at background. so, container will keep on running untill the bash shell process will killed.
To attach to the running background container,use
docker attach b1a0873a8647
if you want to detach from container without exiting(without killing the bash shell),
By default , you can use ctrl-p,q. it will come out of container without exiting from the container(running background. that means without killing the bash shell).
You can pass the custom command during attach time to container,
docker attach --detach-keys="ctrl-s" b1a0873a8647
this time ctrl-p,q escape sequence won't work. instead, ctrl-s will work for exiting from container. you can pass any key eg, (ctrl-*)
You can simply kill docker cli process by sending SEGKILL. If you started the container with
docker run -it some/container
You can get it's pid
ps -aux | grep docker
user 1234 0.3 0.6 1357948 54684 pts/2 Sl+ 15:09 0:00 docker run -it some/container
let's say it's 1234, you can "detach" it with
kill -9 1234
It's somewhat of a hack but it works!
To prevent having logs you should run in detach mode using the -d flag
docker run -d <your_command>
If you are already stuck, you could open a new window/tab in your terminal and close the first one. It won't stop the process of the running job
in case if you using docker on windows, you may use combination 'CTRL + D'
Old post but just exit then start it again... the issue is if you are on a windows machine Ctrl p or Ctrl P are tied to print... exiting the starting the container should not hurt anything