Docker - How to access a volume not attached to a container?

Question

I have (had) a data container which has a volume used by other containers (--volumes-from).

The data container has accidentally been removed.

Thankfully the volume was not removed.

Is there any way I can re run the data container and point it BACK to this volume?

Cyndy

Answer 1

Is there any way can re run the data container and point it BACK to this volume?

Sure, I detailed it in "How to recover data from a deleted Docker container? How to reconnect it to the data?"

You need to create a new container with the same VOLUME (but its path /var/lib/docker/volumes/... would be empty or with an initial content)

Then you move your legacy volume to the path of the volume of the new container.

More generally, whenever I start a data volume container, I register its volume path in a file (to reuse that path later if my container is accidentally removed)

Decastyle

You are a star, sounds like the perfect solution. My only issue now is to try to work out which of the 50 volumes on that machine is the one that i need!! Once that is done Ill use your approach for keeping track of the volume in use. Cheers, m – Cyndy

Answer 2

Not entirely sure but you might try

docker run -i -t --volumes-from yourvolume ubuntu /bin/bash

You should then be able to access the directory, i think.

Embezzle

As long as you've still got "yourvolume" i believe launching any other container with --volumes-from should re-connect. – Embezzle

I still have the volume, but not the container that created it. and the value of --volumes-from is the container name, which no longer exists... – Cyndy

Afraid i have little expertise, only just managed to grasp volumes myself. I'm not quite sure what you mean by you still have the volume. Posting your docker ps -a output may help someone else determine what you can do. – Embezzle

When you create, build and run a docker container with en external volume (data written to the host), you end up with an 'image', 'container' and 'volume'. I have deleted the 'image' and 'container' but the 'volume' is still there. The issue is, once the 'container' that linked to the 'volume' has gone, I cant see how to get back to the 'volume' – Cyndy

Answer 3

When I came to this question, my main concern was data loss. Here is how I copied data from a volume to AWS S3:

# Create a dummy container - I like Python
host$ docker run -it -v my_volume:/datavolume1 python:3.7-slim bash

# Prepare AWS stuff
# executing 'cat ~/.aws/credentials' on your development machine
# will likely show them
python:3.7-slim$ pip install awscli
python:3.7-slim$ export AWS_ACCESS_KEY_ID=yourkeyid
python:3.7-slim$ export AWS_SECRET_ACCESS_KEY=yoursecrectaccesskey

# Copy
python:3.7-slim$ aws s3 cp /datavolume1/thefile.zip s3://bucket/key/thefile.zip

Alternatively you can use aws s3 sync.

MySQL / MariaDB

My specific example was about MySQL / MariaDB. If you want to backup a database of MySQL / MariaDB, just execute

$ mysqldump -u [username] -p [database_name] \
            --single-transaction --quick --lock-tables=false \
            > db1-backup-$(date +%F).sql

You might also want to consider

• --skip-add-drop-table: Skip the table creation if it already exists. Without this flag, the table is dropped.
• --complete-insert: Add the column names. Without this flag, there might be a column mismatch.

To restore the backup:

$ mysql -u [username] -p [database_name] < [filename].sql

Brassard