title: Can packages be shared across Anaconda environments?
body: <p>My <code>~/anaconda</code> directory is taking up too much disk space (10GB), although I have only five environments and have run <code>conda clean</code>. I discovered that when I try to create a new conda environment, Anaconda displays a very long list of packages to be downloaded, which seems to include a full scientific Python stack (Python interpreter, numpy, scipy, etc.). It seems that Anaconda is installing everything independently for each environment. Is this true?</p>
  
  <p>The following list contains some purely speculative ways which could potentially solve the space problem:</p>
  
  <ul>
  <li>Can I create a "sub-environment" which "inherits" the packages of a "parent environment"?</li>
  <li>Can Anaconda be made to share (e.g. via symbolic links on the file system) the same packages used in different environments?</li>
  <li>Does the default environment have any special status in terms of package managing? I use Anaconda 2, but most of my environments use Python 3. Can I save space by switching to Anaconda 3? (This is regarding the default environment as the "parent environment" of all other environments.)</li>
  <li>I normally use <code>pip</code> to install packages, as <code>conda install</code> often fails. Does <code>conda install</code> do some smart job to reuse packages already installed somewhere else?</li>
  </ul>
  
  <p>(Debugging information) The sizes of my four environment directories under <code>~/anaconda/envs</code> are between 1.2GB and 2.6GB. Is this normal?</p>