How to recover data from a deleted Docker container? How to reconnect it to the data?

Question

Let's say, I delete a PostgreSQL docker container which had its data only here:

$ docker inspect postgres1
...
"Source": "/var/lib/docker/volumes/4948af..../_data"
"Destination": "/var/lib/postgresql/data"

$ docker rm postgres1

If there was no other container referencing the volume, I cannot reconnect to this volume with --volumes-from any more, even though the files are still on disk somewhere in: /var/lib/docker/volumes/...

This presents me with two problems:

1. What is the best way to locate the data, if I do not know the volume UUID of the directory?
   • Doing ls /var/lib/docker/volumes/ presents me with a hundred dirs like this f77c92....
   • Using find . -name "*postgres*" I still get dozens of results like this ...10e0dc/_data/postgresql.conf, with no clear way to identify the right one.
2. Once I find the correct data in the directory, how do I reconnect a newly created postgres container to this data in /var/lib/docker/volumes/4948af.../_data

I have a daily full system rsync backup. How could this help in recovery (short of restoring the whole system)?

Answer 1

That is exactly why, when creating a data container, I always register its path in a file. (see my script updateDataContainerPath)

Usage (to be used just after creating a data container):

docker inspect ${gitolite_repos_cont} > /dev/null 2>&1 || docker create --name="${gitolite_repos_cont}" gitolite.repos /bin/true

# source the script, to make the updatePath() function available
. ../updateDataContainerPath

# save the path in a file
updatePath ${gitolite_repos_cont} "$HOME/b2d/gitolite" ${grepos}

(here ${grepos} is the file where you register or save the path of the volume of the data container)

That script will, if there was already a path saved for that data container, remove the empty data container folder, and move the old one to the new one (and update the new path)

sudo rm -Rf "${grpath}"
sudo mv "${fgrpath}" "${grpath}"

That would help answering your question 2, and avoid entirely your question 1.

That way, I can rm any container (including a data container, without the -v option of course), and I know the next time I recreate that same data container, I will find back my data.