How to upgrade docker container after its image ch

Question

Let's say I have pulled the official mysql:5.6.21 image.

I have deployed this image by creating several docker containers.

These containers have been running for some time until MySQL 5.6.22 is released. The official image of mysql:5.6 gets updated with the new release, but my containers still run 5.6.21.

How do I propagate the changes in the image (i.e. upgrade MySQL distro) to all my existing containers? What is the proper Docker way of doing this?

Answer 1

Here's what it looks like using docker-compose when building a custom Dockerfile.

1. Build your custom Dockerfile first, appending a next version number to differentiate. Ex: docker build -t imagename:version . This will store your new version locally.
2. Run docker-compose down
3. Edit your docker-compose.yml file to reflect the new image name you set at step 1.
4. Run docker-compose up -d. It will look locally for the image and use your upgraded one.

-EDIT-

My steps above are more verbose than they need to be. I've optimized my workflow by including the build: . parameter to my docker-compose file. The steps looks this now:

1. Verify that my Dockerfile is what I want it to look like.
2. Set the version number of my image name in my docker-compose file.
3. If my image isn't built yet: run docker-compose build
4. Run docker-compose up -d

I didn't realize at the time, but docker-compose is smart enough to simply update my container to the new image with the one command, instead of having to bring it down first.

Answer 2

Taking from http://blog.stefanxo.com/2014/08/update-all-docker-images-at-once/

You can update all your existing images using the following command pipeline:

docker images | awk '/^REPOSITORY|\<none\>/ {next} {print $1}' | xargs -n 1 docker pull

Answer 3

Consider for this answers:

• The database name is app_schema
• The container name is app_db
• The root password is root123

How to update MySQL when storing application data inside the container

This is considered a bad practice, because if you lose the container, you will lose the data. Although it is a bad practice, here is a possible way to do it:

1) Do a database dump as SQL:

docker exec app_db sh -c 'exec mysqldump app_schema -uroot -proot123' > database_dump.sql

2) Update the image:

docker pull mysql:5.6

3) Update the container:

docker rm -f app_db
docker run --name app_db --restart unless-stopped \
-e MYSQL_ROOT_PASSWORD=root123 \
-d mysql:5.6

4) Restore the database dump:

docker exec app_db sh -c 'exec mysql -uroot -proot123' < database_dump.sql

How to update MySQL container using an external volume

Using an external volume is a better way of managing data, and it makes easier to update MySQL. Loosing the container will not lose any data. You can use docker-compose to facilitate managing multi-container Docker applications in a single host:

1) Create the docker-compose.yml file in order to manage your applications:

version: '2'
services:
  app_db:
    image: mysql:5.6
    restart: unless-stopped
    volumes_from: app_db_data
  app_db_data:
    volumes: /my/data/dir:/var/lib/mysql

2) Update MySQL (from the same folder as the docker-compose.yml file):

docker-compose pull
docker-compose up -d

Note: the last command above will update the MySQL image, recreate and start the container with the new image.

Answer 4

I would like to add that if you want to do this process automatically (download, stop and restart a new container with the same settings as described by @Yaroslav) you can use WatchTower. A program that auto updates your containers when they are changed https://github.com/v2tec/watchtower

Answer 5

Similar answer to above

docker images | awk '{print $1}' | grep -v 'none' | grep -iv 'repo' | xargs -n1 docker pull

Answer 6

After evaluating the answers and studying the topic I'd like to summarize.

The Docker way to upgrade containers seems to be the following:

Application containers should not store application data. This way you can replace app container with its newer version at any time by executing something like this:

docker pull mysql
docker stop my-mysql-container
docker rm my-mysql-container
docker run --name=my-mysql-container --restart=always \
  -e MYSQL_ROOT_PASSWORD=mypwd -v /my/data/dir:/var/lib/mysql -d mysql

You can store data either on host (in directory mounted as volume) or in special data-only container(s). Read more about it here, here, and here.

Upgrading applications (eg. with yum/apt-get upgrade) within containers is considered to be an anti-pattern. Application containers are supposed to be immutable, which shall guarantee reproducible behavior. Some official application images (mysql:5.6 in particular) are not even designed to self-update (apt-get upgrade won't work).

I'd like to thank everybody who gave their answers, so we could see all different approaches.