Surely you don't mean install all available packages, right? Continuum's default channel alone has 635 of them, and there are countless others on other channels.
I think @cel is right above to assume that you're specifically asking to install all of the packages that Continuum includes in its default Anaconda installer. If that's the case, then the simplest command is this:
conda create -n env_full anaconda
This will install the latest version of the anaconda
package set, as compiled for your default version of Python (the one you used to install Anaconda originally). If you'd like to create an environment with a different version of Python, then just add that to the command line; e.g.
conda create -n env_full anaconda python=2.7
conda create -n env_full anaconda python=3.5
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