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    <p>Hi Toni,</p>
    <p>thank you very much for your answer...</p>
    <blockquote type="cite"
      cite="mid:A2B6ED4D-53BB-49E3-A1C3-949BD4C9A2C4@csgis.de"><br>
      <div class="">- Browser cache. (Delete it)</div>
      <div class="">- a not writeable thumbs dir (checkit)</div>
    </blockquote>
    <br>
    thank you for the hints<br>
    I have cleaned the browser cache but the problem is still there: the
    thumbnails exist but they are png images completely white<br>
    The thumbs dir has the following rules<br>
    <br>
    ls -al /var/www/geonode/uploaded/<br>
    <br>
    drwxrwxrwx 4 www-data www-data 4096 nov 24 13:51 .<br>
    drwxr-xr-x 5 www-data root     4096 nov 24 13:50 ..<br>
    drwxrwxrwx 2 www-data www-data 4096 nov 25 19:20 layers<br>
    drwxrwxrwx 2 www-data www-data 4096 nov 26 15:08 thumbs<br>
    <br>
    I think they are fine...<br>
    <br>
    Moreover I have tested that the thumbnails of the maps are correctly
    created and, if I'm not wrong, they are stored in the same folder of
    the layers thumbs <br>
    <br>
    <blockquote type="cite"
      cite="mid:A2B6ED4D-53BB-49E3-A1C3-949BD4C9A2C4@csgis.de"><br>
      <div class="">what else you can do is check the thumbnail url and
        see if the image exists on your</div>
      <div class="">drive.</div>
    </blockquote>
    <br>
    Yes, thank you.<br>
    The files exist but they are white png images<br>
    <br>
    <blockquote type="cite"
      cite="mid:A2B6ED4D-53BB-49E3-A1C3-949BD4C9A2C4@csgis.de">
      <div class="">An easy way is as already suggested to use the
        browser console. Or to navigate</div>
      <div class="">to a layer in django admin: <a
          href="http://yoururl/admin/layers/layer/1/" class=""
          moz-do-not-send="true">http://YOURURL/admin/layers/layer/1/</a></div>
    </blockquote>
    <br>
    yes... the thumb file is there:  
    uploaded/thumbs/layer-40a378c6-d20d-11e7-a6fc-0050568d40c1-thumb.png
    <br>
    <br>
    <br>
    thank you again...<br>
    any idea or strategy for understanding the problem is welcome<br>
    <br>
    best regards<br>
    Ivan<br>
    <br>
    <br>
    <br>
    <blockquote type="cite"
      cite="mid:A2B6ED4D-53BB-49E3-A1C3-949BD4C9A2C4@csgis.de">
      <div class=""><br class="">
      </div>
      <div class="">cheers,</div>
      <div class=""><br class="">
      </div>
      <div class="">Toni</div>
      <div class=""><br class="">
        <div class="">
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            word-wrap: break-word; -webkit-nbsp-mode: space;
            -webkit-line-break: after-white-space;" class="">
            <div style="color: rgb(0, 0, 0); letter-spacing: normal;
              orphans: auto; text-align: start; text-indent: 0px;
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              word-spacing: 0px; -webkit-text-stroke-width: 0px;
              word-wrap: break-word; -webkit-nbsp-mode: space;
              -webkit-line-break: after-white-space;" class="">
              <div style="color: rgb(0, 0, 0); letter-spacing: normal;
                orphans: auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                word-wrap: break-word; -webkit-nbsp-mode: space;
                -webkit-line-break: after-white-space;" class="">
                <div style="color: rgb(0, 0, 0); letter-spacing: normal;
                  orphans: auto; text-align: start; text-indent: 0px;
                  text-transform: none; white-space: normal; widows:
                  auto; word-spacing: 0px; -webkit-text-stroke-width:
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                    break-word; -webkit-nbsp-mode: space;
                    -webkit-line-break: after-white-space;" class="">
                    <div class="">
                      <div style="word-wrap: break-word;
                        -webkit-nbsp-mode: space; -webkit-line-break:
                        after-white-space;" class="">
                        <div class="">
                          <div class="">-----------------------------------------------</div>
                          <div class="">CSGIS</div>
                          <div class=""><br class="">
                          </div>
                          <div class="">-----------------------------------------------</div>
                          <div class="">
                            <div class="" style="orphans: 2; widows: 2;">Kolonnadenstraße
                              1</div>
                            <div class="" style="orphans: 2; widows: 2;">04109
                              Leipzig</div>
                          </div>
                          <div class="">-----------------------------------------------</div>
                          <div class="">Mobil<span class="Apple-tab-span" style="white-space: pre;">  </span>+49/
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                          <div class="">Tel <span class="Apple-tab-span" style="white-space: pre;">          </span>+49/
                            (0) 341 24 04 738</div>
                          <div class="">Fax <span class="Apple-tab-span" style="white-space: pre;">          </span>+49/
                            (0) 341 24 04 73</div>
                          <div class="">Web<span class="Apple-tab-span" style="white-space: pre;">            </span><a
                              href="http://csgis.de" class=""
                              moz-do-not-send="true">http://csgis.de</a></div>
                          <div class="">-----------------------------------------------</div>
                          <div class=""><br class="">
                          </div>
                          <div class="">Hinweis gemäß § 33 BDSG</div>
                          <div class="">Daten der Verfahrensbeteiligten
                            werden gespeichert. Dieses Dokument ist
                            ausschließlich für den </div>
                          <div class="">Adressaten bestimmt. Der Inhalt
                            der E-Mail ist vertraulich. Falls Sie diese
                            E-Mail versehentlich </div>
                          <div class="">erhalten haben, rufen Sie uns
                            unter obiger Rufnummer umgehend an und
                            löschen Sie diese Nachricht </div>
                          <div class="">von Ihrem Computer. Jegliche Art
                            von Reproduktionen, Verbreitung,
                            Vervielfältigung, Veränderung, </div>
                          <div class="">Verteilung und/oder
                            Veröffentlichung dieser E-Mail ist verboten.</div>
                        </div>
                      </div>
                    </div>
                  </div>
                </div>
              </div>
            </div>
          </div>
        </div>
        <br class="">
        <div>
          <blockquote type="cite" class="">
            <div class="">Am 26.11.2017 um 07:13 schrieb <a
                href="mailto:geonode-users-request@lists.osgeo.org"
                class="" moz-do-not-send="true">geonode-users-request@lists.osgeo.org</a>:</div>
            <br class="Apple-interchange-newline">
            <div class=""><span style="font-family: Helvetica;
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                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Message:
                3</span><br style="font-family: Helvetica; font-size:
                12px; font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
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                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Date:
                Sat, 25 Nov 2017 18:19:39 +0100</span><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
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                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">From:
                Ivan Marchesini <</span><a
                href="mailto:ivan.marchesini@gmail.com"
                style="font-family: Helvetica; font-size: 12px;
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                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="" moz-do-not-send="true">ivan.marchesini@gmail.com</a><span
                style="font-family: Helvetica; font-size: 12px;
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                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">></span><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">To:<span
                  class="Apple-converted-space"> </span></span><a
                href="mailto:geonode-users@lists.osgeo.org"
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="" moz-do-not-send="true">geonode-users@lists.osgeo.org</a><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Subject:
                [GeoNode-users] can't see the layers preview in the
                "explore</span><br style="font-family: Helvetica;
                font-size: 12px; font-style: normal; font-variant-caps:
                normal; font-weight: normal; letter-spacing: normal;
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                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
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                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">       layer"
                 page</span><br style="font-family: Helvetica;
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                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
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                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Message-ID:
                <</span><a
                href="mailto:a52ee523-8cc1-b518-5875-bf0f5efaac8e@gmail.com"
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
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                class="" moz-do-not-send="true">a52ee523-8cc1-b518-5875-bf0f5efaac8e@gmail.com</a><span
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">></span><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
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                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Content-Type:
                text/plain; charset=utf-8; format=flowed</span><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <br style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Dear
                Geonode users,</span><br style="font-family: Helvetica;
                font-size: 12px; font-style: normal; font-variant-caps:
                normal; font-weight: normal; letter-spacing: normal;
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                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <br style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">after
                a fresh installation of Geonode 2.6 on ubuntu 16.04 I'm
                doing some</span><br style="font-family: Helvetica;
                font-size: 12px; font-style: normal; font-variant-caps:
                normal; font-weight: normal; letter-spacing: normal;
                orphans: auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">tests
                and it seems I can't see the thumbnail of the uploaded
                layers in</span><br style="font-family: Helvetica;
                font-size: 12px; font-style: normal; font-variant-caps:
                normal; font-weight: normal; letter-spacing: normal;
                orphans: auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">the
                "explore later" page...</span><br style="font-family:
                Helvetica; font-size: 12px; font-style: normal;
                font-variant-caps: normal; font-weight: normal;
                letter-spacing: normal; orphans: auto; text-align:
                start; text-indent: 0px; text-transform: none;
                white-space: normal; widows: auto; word-spacing: 0px;
                -webkit-text-stroke-width: 0px;" class="">
              <br style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">is
                this something that you have already observed?</span><br
                style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <br style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">many
                thanks</span><br style="font-family: Helvetica;
                font-size: 12px; font-style: normal; font-variant-caps:
                normal; font-weight: normal; letter-spacing: normal;
                orphans: auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <br style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;"
                class="">
              <span style="font-family: Helvetica; font-size: 12px;
                font-style: normal; font-variant-caps: normal;
                font-weight: normal; letter-spacing: normal; orphans:
                auto; text-align: start; text-indent: 0px;
                text-transform: none; white-space: normal; widows: auto;
                word-spacing: 0px; -webkit-text-stroke-width: 0px;
                float: none; display: inline !important;" class="">Ivan</span></div>
          </blockquote>
        </div>
        <br class="">
      </div>
    </blockquote>
    <br>
  </body>
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