Use tags to indicate specific versions of an image, if needed. In our how to call a Service image from Docker Hub example, we called:
services: apache: image: tugboatqa/httpd:2.4 msyql: image: tugboatqa/mysql:5.6
In this example, we called versions
5.6 for the
images. These are Docker image version tags.
You can specify version tags in a few different ways:
If you don’t need a specific version of a Service image, you
can leave the tag off of the image call. When you don’t specify a tag, you’ll
get the latest version of that image. However, because
latest pulls the newest
version of an image, it could introduce a breaking change, so we recommend
specifying major/minor versions as needed.
If you’re not sure which version tag to use, you can always browse to the service image on Docker Hub and check out what tags are available.
Using specific version tags helps prevent breaking changes that come along with
incremental updates. In our example above, we’ve called
If you want to make sure you’re using a specific major version, but don’t care
about point releases, specify something like
tugboatqa/node:10 to ensure you
always use the latest available minor release of node 10.x.
In some cases, you’re less likely to be worried about a specific version; for example, it may not matter which version of memcached you use.
When you don’t need to call for a specific version of a Service, using the image
name without a tag (
tugboatqa/memcached), or the
tugboatqa/memcached:latest) will get you the most recent version of a Service