unshare --pid /bin/bash - fork cannot allocate memory : <p>I'm experimenting with linux namespaces.  Specifically the pid namespace.</p>

<p>I thought I'd test something out with bash but run into this problem:</p>

<pre><code>unshare -p /bin/bash
bash: fork: Cannot allocate memory
</code></pre>

<p>Running ls from there gave a core dump.  Exit is the only thing possible.</p>

<p>Why is it doing that?</p>
