This Docker get you sitespeed.io with Chrome and Firefox installed.
The --rm -v "$(pwd)":/sitespeed.io will make the result HTML stored on your host.
docker run --privileged --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io http://www.sitespeed.io/ -b chrome
docker run --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io s http://www.sitespeed.io/ -b firefox
Always run sitespeed.io on specific version (always do that with Docker) meaning specify the tag after your container name. Then you have control of what versions you are using (both of sitespeed.io and the browsers). In practice, this means you should run it like this:
docker run --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io:4.0.0 http://www.sitespeed.io/ -b firefox
If you not use the tag after the container, the latest version will be downloaded and you will not have full control of the exact version.
sitespeed.io is highly configurable, check the documentation.
Say there's a new release of sitespeed.io and you want to run that, how do you do that? First check the changelog. Are there any changes that will break what you do? If not, just pull the new version (change X.Y.Z to the version you want to use):
docker pull sitespeedio/sitespeed.io:X.Y.Z
And then change where you start your container like this:
docker run --rm -v "$(pwd)":/sitespeed.io sitespeedio/sitespeed.io:X.Y.Z ...