The release of Docker 1.8 introduces big changes, aimed at meeting user demand to comprise smaller, standalone components.
Docker 1.8 offers support for image signing and a new installer, along with incremental improvements to Engine, Compose, Swarm, Machine and Registry.
Earlier this year, Docker announced that runC would be released as a separate element, and Docker 1.8 comes closer to that goal.
The Docker 1.8 system powering image signing is now a separate component, dubbed Notary. The volume plugins that were an experimental feature in Docker 1.7 are a stable part of that release.
The large-scale changes made for Docker 1.8 are accompanied by the regular upgrades aimed at increasing Docker quality and making the container platform more user friendly.
Docker Engine 1.8 comes with the new Docker Content Trust and The Update Framework (TUF), making it possible to verify the publisher of Docker images.
When an image is published, Docker creates a key specific to the publisher. When the image is pulled later, Docker uses the publisher’s public key to verify that the image being run is what the publisher created, that the image has not been tampered with and that the image is up to date.
The release of Docker 1.8 also is accompanied by new installers for Mac OS X and Windows called Docker Toolbox.
Toolbox provides the fastest way to get up and running with a Docker development environment by installing everything a Docker user needs, including Docker client, Machine and VirtualBox. For Mac users, Toolbox also installs Compose.
Docker 1.7 included experimental support for volume plugins that allowed users to back Docker volumes with any third-part storage system.
With Docker 1.8, Volume plugins are in Engine’s stable build, and storage systems have been integrated into Docker. Plugins are available from Docker partners, including Blockbridge, Ceph, ClusterHQ, EMC and Portworx.
Engine 1.6 included the addition of logging drivers, which allowed users to ship logs from containers straight to logging systems like syslogd. Docker now has added more systems, including GELF, Fluentd and a driver that will rotate users’ on-disk logs.
Other user-friendly features added for Docker 1.8 include:
* The ability to copy files from host to container. Previously, `docker cp` would copy files from a container out to the host. With `docker cp foo.txt mycontainer:/foo.txt`, files can be copied in reverse.
* The new docker daemon command now is used to run the daemon, rather than passing the -d flag. This change makes it clear which command-line options are for client (docker –help) and which are for daemon (`docker daemon –help`).
* A customisable ps format. With docker ps, there now is a `–format` option that can be used to customise a command’s output.
* A configurable client config directory. The Docker client stores some config files in `~/.docker`. For users who need to run multiple clients on a single machine, they can now configure with `–config` and the `DOCKER_CONFIG` environment variable.