I lose my data when the container exits

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.

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.

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

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