title: ZFS. Unmount duplicated entries
body: <p>After some unsuccessful experiments with zfs snapshots I see following output for 'zfs list':</p>
  
  <pre><code>$ zfs list
  NAME                                    USED  AVAIL  REFER  MOUNTPOINT
  tank                                   1.48T  2.64T  25.4K  none
  tank/home                              92.6K  2.64T  92.6K  legacy
  tank/jails                             1.46T  2.64T  41.1K  legacy
  tank/jails/jail05                      18.3G  2.64T  17.7G  /jails/jail05
  tank/jails/jail06                      18.3G  2.64T  17.7G  /jails/jail06
  tank/jails/somefldr                    18.3G  2.64T  17.7G  /jails/jail06
  </code></pre>
  
  <p>Now there are two mountpoints with the same name (<strong>/jails/jail06</strong>) pointing to different zfs directories. 
  The zfs unmount command doesn't work.</p>
  
  <pre><code>$ sudo zfs unmount /jails/jail06
  cannot unmount '/jails/jail06': not a mountpoint
  </code></pre>
  
  <p>Looking for any advice to solve this issue. Thanks in advance!</p>
  
  <p>Upd:</p>
  
  <pre><code>zfs mount
  </code></pre>
  
  <p>displays no <strong>/jails/jail06</strong> mounted.</p>