I lose my data when the container exits

Question

Despite Docker's Interactive tutorial and faq I lose my data when the container exits.

I have installed Docker as described here: http://docs.docker.io/en/latest/installation/ubuntulinux without any problem on ubuntu 13.04.

But it loses all data when exits.

iman@test:~$ sudo docker version
Client version: 0.6.4 
Go version (client): go1.1.2 
Git commit (client): 2f74b1c 
Server version: 0.6.4 
Git commit (server): 2f74b1c 
Go version (server): go1.1.2 
Last stable version: 0.6.4 


iman@test:~$ sudo docker run ubuntu ping
2013/10/25 08:05:47 Unable to locate ping 
iman@test:~$ sudo docker run ubuntu apt-get install ping
Reading package lists... 
Building dependency tree... 
The following NEW packages will be installed: 
  iputils-ping 
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. 
Need to get 56.1 kB of archives. 
After this operation, 143 kB of additional disk space will be used. 
Get:1 http://archive.ubuntu.com/ubuntu/ precise/main iputils-ping amd64 3:20101006-1ubuntu1 [56.1 kB] 
debconf: delaying package configuration, since apt-utils is not installed 
Fetched 56.1 kB in 0s (195 kB/s) 
Selecting previously unselected package iputils-ping. 
(Reading database ... 7545 files and directories currently installed.) 
Unpacking iputils-ping (from .../iputils-ping_3%3a20101006-1ubuntu1_amd64.deb) ... 
Setting up iputils-ping (3:20101006-1ubuntu1) ... 
iman@test:~$ sudo docker run ubuntu ping
2013/10/25 08:06:11 Unable to locate ping 
iman@test:~$ sudo docker run ubuntu touch /home/test
iman@test:~$ sudo docker run ubuntu ls /home/test
ls: cannot access /home/test: No such file or directory 

I also tested it with interactive sessions with the same result. Did I forget something?

EDIT: IMPORTANT FOR NEW DOCKER USERS

As @mohammed-noureldin and others said, actually this is NOT a container exiting. Every time it just creates a new container.

Answer 1

You need to commit the changes you make to the container and then run it. Try this:

sudo docker pull ubuntu

sudo docker run ubuntu apt-get install -y ping

Then get the container id using this command:

sudo docker ps -l

Commit changes to the container:

sudo docker commit <container_id> iman/ping 

Then run the container:

sudo docker run iman/ping ping www.google.com

This should work.

Answer 2

When you use docker run to start a container, it actually creates a new container based on the image you have specified.

Besides the other useful answers here, note that you can restart an existing container after it exited and your changes are still there.

docker start f357e2faab77 # restart it in the background
docker attach f357e2faab77 # reattach the terminal & stdin

Answer 3

There are following ways to persist container data:

1. Docker volumes

2. Docker commit

   a) create container from ubuntu image and run a bash terminal.

      $ docker run -i -t ubuntu:14.04 /bin/bash
   

   b) Inside the terminal install curl

      # apt-get update
      # apt-get install curl
   

   c) Exit the container terminal

      # exit
   

   d) Take a note of your container id by executing following command :

      $ docker ps -a
   

   e) save container as new image

      $ docker commit <container_id> new_image_name:tag_name(optional)
   

   f) verify that you can see your new image with curl installed.

      $ docker images           
   
      $ docker run -it new_image_name:tag_name bash
         # which curl
           /usr/bin/curl
   

Answer 4

In addition to Unferth's answer, it is recommended to create a Dockerfile.

In an empty directory, create a file called "Dockerfile" with the following contents.

FROM ubuntu
RUN apt-get install ping
ENTRYPOINT ["ping"]

Create an image using the Dockerfile. Let's use a tag so we don't need to remember the hexadecimal image number.

$ docker build -t iman/ping .

And then run the image in a container.

$ docker run iman/ping stackoverflow.com

Answer 5

I have got a much simpler answer to your question, run the following two commands

sudo docker run -t -d ubuntu --name mycontainername /bin/bash
sudo docker ps -a

the above ps -a command returns a list of all containers. Take the name of the container which references the image name - 'ubuntu' . docker auto generates names for the containers for example - 'lightlyxuyzx', that's if you don't use the --name option.

The -t and -d options are important, the created container is detached and can be reattached as given below with the -t option.

With --name option, you can name your container in my case 'mycontainername'.

sudo docker exec -ti mycontainername bash

and this above command helps you login to the container with bash shell. From this point on any changes you make in the container is automatically saved by docker. For example - apt-get install curl inside the container You can exit the container without any issues, docker auto saves the changes.

On the next usage, All you have to do is, run these two commands every time you want to work with this container.

This Below command will start the stopped container:

sudo docker start mycontainername

sudo docker exec -ti mycontainername bash

Another example with ports and a shared space given below:

docker run -t -d --name mycontainername -p 5000:5000 -v ~/PROJECTS/SPACE:/PROJECTSPACE 7efe2989e877 /bin/bash

In my case: 7efe2989e877 - is the imageid of a previous container running which I obtained using

docker ps -a

Answer 6

There are really great answers above to the asked question. There might be no need for another answer but still I want to give my personal opinion on the topic in the simplest words possible.

Here are some points about containers & images that will help us for a conclusion:

• A docker image can be:
  1. created-from-a-given-container
  2. deleted
  3. used-to-create-any-number-of-containers
• A docker container can be:
  1. created-from-an-image
  2. started
  3. stopped
  4. restarted
  5. deleted
  6. used-to-create-any-number-of-images
• A docker run command does this:
  1. Downloads an image or uses a cached image
  2. Creates a new container out of it
  3. Starts the container
• When a Dockerfile is used to create an image:
  1. It is already well known that the image will eventually be used to run a docker container.
  2. After issuing docker build command, docker behind-the-scenes creates a running container with a base-file-system and follows steps inside the Dockerfile to configure that container as per the developers need.
  3. After the container is configured with specs of the Dockerfile, it will be committed as an image.
  4. The image gets ready to rock & roll!

Conclusion:

As we can see, a docker container is independent of a docker image.

A container can be restarted provided the unique ID of that container [use docker ps --all to get the id].

Any operation like making a new directory, creating files, installing tools, etc. can be done inside the container when it is running. Once the container is stopped, it persists all the changes. Container stopping and restarting is like rebooting a computer system.

An already created container is always available for a restart but when we issue docker run command, a new container is created out of an image and hence it is like a new computer system. The changes made inside the old container - as we can understand now - are not available in this new container.

A final note:

I guess it's now obvious why the data seems to be lost yet it is always there.. but in a different [old] container. So, take a good note of the difference in docker start & docker run command & never get confused in them.

Answer 7

You might want to look at docker volumes if you you want to persist the data in your container. Visit https://docs.docker.com/engine/tutorials/dockervolumes/. The docker documentation is a very good place to start

Answer 8

My suggestion is to manage docker, with docker compose. Is an easy to way to manage all the docker's containers for your project, you can map the versions and link different containers to work together.

The docs are very simple to understand, better than docker's docs.

Docker-Compose Docs

Best

Answer 9

the similar problem (and no way Dockerfile alone could fix it) brought me to this page.

stage 0: for all, hoping Dockerfile could fix it: until --dns and --dns-search will appear in Dockerfile support - there is no way to integrate intranet based resources into.

stage 1: after building image using Dockerfile (by the way it's a serious glitch Dockerfile must be in the current folder), having an image to deploy what's intranet based, by running docker run script. example: docker run -d \ --dns=${DNSLOCAL} \ --dns=${DNSGLOBAL} \ --dns-search=intranet \ -t pack/bsp \ --name packbsp-cont \ bash -c " \ wget -r --no-parent http://intranet/intranet-content.tar.gz \ tar -xvf intranet-content.tar.gz \ sudo -u ${USERNAME} bash --norc"

stage 2: applying docker run script in daemon mode providing local dns records to have ability to download and deploy local stuff.

important point: run script should be ending with something like /usr/bin/sudo -u ${USERNAME} bash --norc to keep container running even after the installation scripts finishes.

no, it's not possible to run container in interactive mode for the full automation matter as it will remain inside internal shall command prompt until CTRL-p CTRL-q being pressed.

no, if interacting bash will not be executed at the end of the installation script, the container will terminate immediately after finishes script execution, loosing all installation results.

stage 3: container is still running in background but it's unclear whether container has ended installation procedure or not yet. using following block to determine execution procedure finishes: while ! docker container top ${CONTNAME} | grep "00[[:space:]]\{12\}bash \--norc" - do echo "." sleep 5 done the script will proceed further only after completed installation. and this is the right moment to call: commit, providing current container id as well as destination image name (it may be the same as on the build/run procedure but appended with the local installation purposes tag. example: docker commit containerID pack/bsp:toolchained. see this link on how to get proper containerID

stage 4: container has been updated with the local installs as well as it has been committed into newly assigned image (the one having purposes tag added). it's safe now to stop container running. example: docker stop packbsp-cont

stage5: any moment the container with local installs require to run, start it with the image previously saved. example: docker run -d -t pack/bsp:toolchained

Answer 10

a brilliant answer here How to continue a docker which is exited from user kgs

docker start $(docker ps -a -q --filter "status=exited")
(or in this case just docker start $(docker ps -ql) 'cos you don't want to start all of them)

docker exec -it <container-id> /bin/bash

That second line is crucial. So exec is used in place of run, and not on an image but on a containerid. And you do it after the container has been started.