So, you have a container, made some changes, and want to keep all your hard work. Unless you commit the changes, the next time you open the container it will lose them.
For example, creating a user:
I created the user 'andy' and set a password, and switched
to the user, then created a file.
However, if I exit and restart the container, the change is
lost:
When you exit a container, docker creates an entry in a
process list.
In order to commit the changes, you need to identify the
process id and save it.
The command for this is ps –a:
Restart the container add the user:
Exit from the container and find the last image ID.
Commit the change to this container:
Note I've added a tag to the end of the name of the
container – this is how you manage versions. So I have a container that is
unchanged, and I've created one with a tag called 'latest' – this is the one
with the change.
Tip: After a while there will be loads of entries in the 'ps
–a' list, use this to clean them out:
So now I start the new container using the tag, and the changes
will be there:
All the containers are kept on your local machine, but if
you create a repository you can store them there and share them with others.
You can create a cloud repository in Docker for free.
Create an id
A verification mail will be sent, click on the link, then
sign in.
After logging in, ignore most of the page, but at the top left
click on 'Repositories':
It will be empty, so create one:
Give it a name, the same as the name of your container, and
click 'create'
In this example, I've created one for Centos:
So you have a repository, but nothing in it.
Go back to your docker command line, and you can upload the
container you created with the added user:
Login to the repository:
To upload, you first tag the image, then use the 'push'
command:
The container is now in the cloud repository (note that it
takes a while to show up – the Docker cloud is pretty slow).
However, if the push command came back with no errors, the
container will be there.
Downloading a container
Suppose you mess up your local copy. You can delete the
local image(s) and pull one down from the repository.
If you try before deleting the local copy, it won't do
anything because it's up to date, so delete it first:
Note the 'centos' shown here is the unchanged one without
the added user. Delete it if you like.
So, now get the version you uploaded to the repository, even
though the web page doesn't show it:
The image is there, and can be started:
And the changes are there:
Next time, using an Oracle database inside a container.
