Portage vs Docker

WIth portage you can decide and customize which dependencies to install through some thing called USE flags. These are keywords that when defined, will tell Portage that you want support for the chosen keyword.

Portage uses a sandbox as a safety measure during build processes. This is done to ensure that no packages accidentally write outside a 'safe' location.

Slotting is a feature which allows users to install multiple versions of a software simultaneously. This is especially useful for libraries which have changed interfaces between versions.

With portage you can either compile packages from source or you can download and install their binary versions.

Adding supplemental repositories, aka overlays, is easy with eselect-repository or layman.

If you need faster resolution, you can run pkgcore for search and portage for installing, and they work well together.

By default, portage doesn't delete or move any customized config files, thus enabling competent users to modify any config file however they want.

With portage you can view a list of all the programs that you can install by going to /usr/portage and running ls.

You can fully control all packages if you use it properly.

Docker creates a single object, containing an application with its dependencies, that can be moved between any docker-enabled machines, guaranteeing the same environment for application execution.

Docker tracks changes in systems. It allows for commits and rollbacks and for quick deployment due to having to deploy only the updated code.

Docker essentially allows creating boilerplate systems (a LAMP stack, for example) that can be used as a starting point on multiple projects. And you can find multiple such containers already created by people in their public registry.

Allows automatically assembling a container from its source code.

Docker allows easily pushing and pulling containers to and from their public index.docker.io registry. Additionally, dotCloud maintains a list of official repositories of the more popular containers.

You can set up Docker within an already virtualized environment such as a virtual machine. This allows you to run Docker on Mac and Windows, among other use-cases.

Docker can be used with OpenVZ, systemd-nspawn, libvirt-lxc, libvirt-sandbox, qemu/kvm, BSD Jails, Solaris Zones, and chroot.