mini-ndn

mnndn has used popen for years.
The trick is passing privateDirs to mininet.node.Host constructor, so that $HOME can keep its default value of /root and does not need to be overridden.

Popen does not seem to work correctly for cluster, even when HOME environment is passed:

Mininet Cluster Edition implements RemoteMixin._popen as follows:

    def _popen( self, cmd, sudo=True, tt=True, **params):
        if self.isRemote:
            if sudo:
                cmd = [ 'sudo', '-E' ] + cmd
            if tt:
                cmd = self.sshcmd + cmd
            else:
                # Hack: remove -tt
                sshcmd = list( self.sshcmd )
                sshcmd.remove( '-tt' )
                cmd = sshcmd + cmd
        else:
            if self.user and not sudo:
                # Drop privileges
                cmd = [ 'sudo', '-E', '-u', self.user ] + cmd
        popen = super( RemoteMixin, self )._popen( cmd, **params )
        return popen

When you pass env to node.popen, the environment variables apply to "ssh" process, but the remote command (such as /usr/bin/nfd) does not receive them.
You could set environment variables in the command line before passing them to node.popen, but it's better to patch RemoteMixin._popen with this feature and send a pull request.