Docker - Container is not running

I'm completely a newbie to docker. I tried to start a exited container like follows,

1. I listed down all available containers using docker ps -a. It listed the following:

   

2. I entered the following commands to start the container which is in the exited stage and enter into the terminal of that image.

   docker start 79b3fa70b51d
   docker exec -it 79b3fa70b51d /bin/sh
   

3. It is throwing the following error.

   FATA[0000] Error response from daemon: Container 79b3fa70b51d is not running

But when I start the container using docker start 79b3fa70b51d. It throws the container ID as output which is normal if it have everything work normally. I'm not sure what causes this error. Any idea about the causes and suggestions about this would be greatly helpful for me. Thanks in advance.

Solution 1:

By default, docker container will exit immediately if you do not have any task running on the container.

To keep the container running in the background, try to run it with --detach (or -d) argument.

For examples:

docker pull debian

docker run -t -d --name my_debian debian
e7672d54b0c2

docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
e7672d54b0c2        debian              "bash"              3 minutes ago       Up 3 minutes                            my_debian

#now you can execute command on the container
docker exec -it my_debian bash
root@e7672d54b0c2:/# 

Solution 2:

Container 79b3fa70b51d seems to only do an echo.

That means it starts, echo and then exits immediately.

The next docker exec command wouldn't find it running in order to attach itself to that container and execute any command: it is too late. The container has already exited.

The docker exec command runs a new command in a running container.

The command started using docker exec will only run while the container's primary process (PID 1) is running

Solution 3:

If it's not possible to start the main process again (for long enough), there is also the possibility to commit the container to a new image and run a new container from this image. While this is not the usual best practice workflow (the new image is not repeatable), I find it really useful to debug a failing script once in a while.

docker exec -it 6198ef53d943 bash
Error response from daemon: Container 6198ef53d9431a3f38e8b38d7869940f7fb803afac4a2d599812b8e42419c574 is not running

docker commit 6198ef53d943
sha256:ace7ca65e6e3fdb678d9cdfb33a7a165c510e65c3bc28fecb960ac993c37ef33

docker run -it ace7ca65e6e bash
root@72d38a8c787d:/#

Solution 4:

This happens with images for which the script does not launch a service awaiting requests, therefore the container exits at the end of the script.

This is typically the case with most base OS images (centos, debian, etc.), or also with the node images.

Your best bet is to run the image in interactive mode. Example below with the node image:

docker run -it node /bin/bash

Output is

root@cacc7897a20c:/# echo $SHELL
/bin/bash