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    <div class="moz-cite-prefix">Dean</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">Here is a an output from a login
      attempt. The account name on both machines is joe.<br>
    </div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix"><tt>$ ssh -v <server></tt><tt><br>
      </tt><tt>OpenSSH_7.6p1 Ubuntu-4ubuntu0.3, OpenSSL 1.0.2n  7 Dec
        2017</tt><tt><br>
      </tt><tt>debug1: Reading configuration data /home/joe/.ssh/config</tt><tt><br>
      </tt><tt>debug1: /home/joe/.ssh/config line 1: Applying options
        for *</tt><tt><br>
      </tt><tt>debug1: Reading configuration data /etc/ssh/ssh_config</tt><tt><br>
      </tt><tt>debug1: /etc/ssh/ssh_config line 19: Applying options for
        *</tt><tt><br>
      </tt><tt>debug1: Connecting to <server> [ip.address of
        server] port 22.</tt><tt><br>
      </tt><tt>debug1: Connection established.</tt><tt><br>
      </tt><tt>debug1: identity file /home/joe/.ssh/id_rsa_halley type 0</tt><tt><br>
      </tt><tt>debug1: key_load_public: No such file or directory</tt><tt><br>
      </tt><tt>debug1: identity file /home/joe/.ssh/id_rsa_halley-cert
        type -1</tt><tt><br>
      </tt><tt>debug1: Local version string SSH-2.0-OpenSSH_7.6p1
        Ubuntu-4ubuntu0.3</tt><tt><br>
      </tt><tt>debug1: Remote protocol version 2.0, remote software
        version OpenSSH_7.9p1 Debian-10+deb10u1</tt><tt><br>
      </tt><tt>debug1: match: OpenSSH_7.9p1 Debian-10+deb10u1 pat
        OpenSSH* compat 0x04000000</tt><tt><br>
      </tt><tt>debug1: Authenticating to <server>:22 as 'joe'</tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_KEXINIT sent</tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_KEXINIT received</tt><tt><br>
      </tt><tt>debug1: kex: algorithm: curve25519-sha256</tt><tt><br>
      </tt><tt>debug1: kex: host key algorithm: ecdsa-sha2-nistp256</tt><tt><br>
      </tt><tt>debug1: kex: server->client cipher:
        <a class="moz-txt-link-abbreviated" href="mailto:chacha20-poly1305@openssh.com">chacha20-poly1305@openssh.com</a> MAC: <implicit> compression:
        none</tt><tt><br>
      </tt><tt>debug1: kex: client->server cipher:
        <a class="moz-txt-link-abbreviated" href="mailto:chacha20-poly1305@openssh.com">chacha20-poly1305@openssh.com</a> MAC: <implicit> compression:
        none</tt><tt><br>
      </tt><tt>debug1: expecting SSH2_MSG_KEX_ECDH_REPLY</tt><tt><br>
      </tt><tt>debug1: Server host key: ecdsa-sha2-nistp256
        SHA256:QV8T212i8K1hhd5P4GVpOFHsOtSDhA30GIlfRug/03c</tt><tt><br>
      </tt><tt>The authenticity of host '<server> (ip.address of
        server)' can't be established.</tt><tt><br>
      </tt><tt>ECDSA key fingerprint is
        SHA256:QV8T212i8K1hhd5P4GVpOFHsOtSDhA30GIlfRug/03c.</tt><tt><br>
      </tt><tt>Are you sure you want to continue connecting (yes/no)?
        yes</tt><tt><br>
      </tt><tt>Warning: Permanently added '<server>,ip.address of
        server' (ECDSA) to the list of known hosts.</tt><tt><br>
      </tt><tt>debug1: rekey after 134217728 blocks</tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_NEWKEYS sent</tt><tt><br>
      </tt><tt>debug1: expecting SSH2_MSG_NEWKEYS</tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_NEWKEYS received</tt><tt><br>
      </tt><tt>debug1: rekey after 134217728 blocks</tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_EXT_INFO received</tt><tt><br>
      </tt><tt>debug1: kex_input_ext_info:
server-sig-algs=<ssh-ed25519,ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521></tt><tt><br>
      </tt><tt>debug1: SSH2_MSG_SERVICE_ACCEPT received</tt><tt><br>
      </tt><tt>debug1: Authentications that can continue:
        publickey,password</tt><tt><br>
      </tt><tt>debug1: Next authentication method: publickey</tt><tt><br>
      </tt><tt>debug1: Offering public key: RSA
        SHA256:cxe0DjCO0G8l1o5GygqKYyG0kgDEPA2K9In3zFvuRsw </tt><tt><br>
      </tt><tt>debug1: Server accepts key: pkalg rsa-sha2-512 blen 535</tt><tt><br>
      </tt><tt>debug1: Authentication succeeded (publickey).</tt><tt><br>
      </tt><tt>Authenticated to <server> ([ip.address of
        server]:22).</tt><tt><br>
      </tt><tt>debug1: channel 0: new [client-session]</tt><tt><br>
      </tt><tt>debug1: Requesting <a class="moz-txt-link-abbreviated" href="mailto:no-more-sessions@openssh.com">no-more-sessions@openssh.com</a></tt><tt><br>
      </tt><tt>debug1: Entering interactive session.</tt><tt><br>
      </tt><tt>debug1: pledge: network</tt><tt><br>
      </tt><tt>packet_write_wait: Connection to ip.address of server
        port 22: Broken pipe</tt></div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">And the relevant lines from
      /var/log/auth.log from the server for that login attempt, just in
      case they help:</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix"><tt>Dec 18 09:29:56 <server>
        sshd[11051]: rexec line 86: Deprecated option UseLogin</tt><tt><br>
      </tt><tt>Dec 18 09:29:56 <server> sshd[11051]: Connection
        closed by <ip.address of client> port 45462 [preauth]</tt><tt><br>
      </tt><tt>Dec 18 09:30:15 <server> sshd[11091]: rexec line
        86: Deprecated option UseLogin</tt><tt><br>
      </tt><tt>Dec 18 09:30:25 <server> sshd[11091]: Connection
        closed by <ip.address of client> port 45468 [preauth]</tt><tt><br>
      </tt><tt>Dec 18 09:30:28 <server> sshd[11110]: rexec line
        86: Deprecated option UseLogin</tt><tt><br>
      </tt><tt>Dec 18 09:30:31 <server> sshd[11110]: Accepted
        publickey for joe from <ip.address for client> port 45470
        ssh2: RSA SHA256:cxe0DjCO0G8l1o5GygqKYyG0kgDEPA2K9In3zFvuRsw</tt><tt><br>
      </tt><tt>Dec 18 09:30:31 <server> sshd[11110]: fatal:
        privsep_preauth: preauth child terminated by signal 31</tt><tt><br>
      </tt><br>
    </div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">Hope that helps identifying the cause
      of the problem. Happy to provide more verbose output if required,
      or config files if required.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">Cheers.</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">Joe Aquilina</div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix"><br>
    </div>
    <div class="moz-cite-prefix">On 17/12/19 7:07 pm, Dean Bergin wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CACCjKfRbARuwnKM=OdZ3=L8g6Wtrbk5b8L7cjmPtgJrgAX1Gcg@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="auto">Hello Joe,
        <div dir="auto"><br>
        </div>
        <div dir="auto">Ok, can you post sanitised vvv(v) output from a
          login attempt?</div>
        <div dir="auto"><br>
        </div>
        <div dir="auto">Also, do you have console or out of band
          management access? You may want to check the server logs as
          well (if you haven't already) and consider increasing
          verbosity there too.</div>
        <div dir="auto"><br>
        </div>
        <div dir="auto">I'm happy to take a look at sanitised logs
          (preferably filtered to just SSH) but no guarantees I can
          pinpoint the problem.</div>
        <div dir="auto">Just hoping to spot wny clues that would hint at
          what the next step is in troubleshooting.</div>
        <div dir="auto"><br>
        </div>
        <div dir="auto"><br>
        </div>
        <div dir="auto">Kind Regards,</div>
        <div dir="auto"><br>
        </div>
        <div dir="auto"><i>Dean Bergin</i>.</div>
      </div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">On Tue, 17 Dec 2019, 18:10 Joe
          Aquilina, <<a href="mailto:joe@chem.com.au"
            moz-do-not-send="true">joe@chem.com.au</a>> wrote:<br>
        </div>
        <blockquote class="gmail_quote" style="margin:0 0 0
          .8ex;border-left:1px #ccc solid;padding-left:1ex">
          <div>
            <div>Dean</div>
            <div><br>
            </div>
            <div>Yes, I have tried using the IPQoS throughput option,
              with no success.</div>
            <div><br>
            </div>
            <div>I have used -v(vv) when logging in, and am happy to
              provide examples when I login, but my knowledge is not
              good enough to be able to decipher what the extra
              verbosity is telling me.<br>
            </div>
            <div><br>
            </div>
            <div>Cheers.</div>
            <div><br>
            </div>
            <div>Joe Aquilina<br>
            </div>
            <div><br>
            </div>
            <div>On 17/12/19 4:55 pm, Dean Bergin wrote:<br>
            </div>
            <blockquote type="cite">
              <div dir="auto">Hello Joe,
                <div dir="auto"><br>
                </div>
                <div dir="auto">Have you tried SSH with the IPQoS
                  throughout option? The following article suggested it
                  (follow link from the post therein).</div>
                <div dir="auto"><br>
                </div>
                <div dir="auto">Also, try increasing SSH verbosity with
                  more  v's ;-)</div>
                <div dir="auto"><br>
                </div>
                <div dir="auto"><a
                    href="https://bbs.archlinux.org/viewtopic.php?id=239982"
                    target="_blank" rel="noreferrer"
                    moz-do-not-send="true">https://bbs.archlinux.org/viewtopic.php?id=239982</a><br>
                </div>
                <div dir="auto"><br>
                </div>
                <div dir="auto">Hope that helps.</div>
                <div dir="auto"><br>
                </div>
                <div dir="auto"><br>
                </div>
                <div dir="auto">Kind Regards,</div>
                <div dir="auto"><br>
                </div>
                <div dir="auto"><i>Dean Bergin</i>.</div>
              </div>
              <br>
              <div class="gmail_quote">
                <div dir="ltr" class="gmail_attr">On Tue, 17 Dec 2019,
                  16:18 Joe Aquilina, <<a
                    href="mailto:joe@chem.com.au" target="_blank"
                    rel="noreferrer" moz-do-not-send="true">joe@chem.com.au</a>>
                  wrote:<br>
                </div>
                <blockquote class="gmail_quote" style="margin:0 0 0
                  .8ex;border-left:1px #ccc solid;padding-left:1ex">
                  <div>
                    <div>Ben</div>
                    <div><br>
                    </div>
                    <div>Thanks for that, and here goes:</div>
                    <div><br>
                    </div>
                    <div>We have two Debian systems here, along with a
                      bunch of Kubuntu and Windows systems. Early last
                      week I upgraded the second of our Debian systems
                      from stretch to buster. A few days earlier, I had
                      upgraded the other Debian system, also from
                      stretch to buster. That first upgrade went fine
                      and everything is working as expected.</div>
                    <div><br>
                    </div>
                    <div>However the second (of course the more
                      important system) did not upgrade correctly. It is
                      mostly ok, but I am unable to ssh in to that
                      machine. When I try to, I get this:</div>
                    <div><br>
                    </div>
                    <div>packet_write_wait: Connection to 10.0.2.1 port
                      22: Broken pipe</div>
                    <div><br>
                    </div>
                    <div>Searching on the net suggested I try adding
                      ServerAliveInterval and ServerAliveCountMax into
                      the sshd_config file - no luck there.<br>
                    </div>
                    <div><br>
                    </div>
                    <div>I have tried removing (and purging) openssh
                      again with no luck.</div>
                    <div><br>
                    </div>
                    <div>I have also tried disabling ufw in case there
                      problem was there, no luck.<br>
                    </div>
                    <div><br>
                    </div>
                    <div>Stopping ssh and sshd services and installing
                      dropbear allows me to login to the machine, and I
                      can perform normal file operations. However, this
                      machine collects and distributes our emails for
                      all users on our LAN and the other machines can't
                      access the machine. There is another (off-site)
                      Debian machine that does an important overnight
                      folder sync which it is currently unable to do as
                      it can't ssh in.<br>
                    </div>
                    <div><br>
                    </div>
                    <div>My Linux/Debian knowledge is obviously pretty
                      limited, and I am not sure what to try next.<br>
                    </div>
                    <div><br>
                    </div>
                    <div>What else can I provide that might help me
                      solve this?</div>
                    <div><br>
                    </div>
                    <div>Sorry to be a bit longwinded and possibly not
                      precise enough in my description of the problem.
                      Thanks in advance for any suggestions, advice or
                      assistance.</div>
                    <div><br>
                    </div>
                    <div>Cheers.</div>
                    <div><br>
                    </div>
                    <div>Joe Aquilina<br>
                    </div>
                    <div><br>
                    </div>
                    <div>On 17/12/19 3:55 pm, Benjamin wrote:<br>
                    </div>
                    <blockquote type="cite">
                      <div dir="ltr">Hi Joe,
                        <div><br>
                        </div>
                        <div>Yep, sounds good to me...</div>
                        <div>~ B</div>
                        <div>(PLUG President)</div>
                      </div>
                      <br>
                      <div class="gmail_quote">
                        <div dir="ltr" class="gmail_attr">On Tue, Dec
                          17, 2019 at 2:57 PM Joe Aquilina <<a
                            href="mailto:joe@chem.com.au"
                            rel="noreferrer noreferrer" target="_blank"
                            moz-do-not-send="true">joe@chem.com.au</a>>
                          wrote:<br>
                        </div>
                        <blockquote class="gmail_quote"
                          style="margin:0px 0px 0px
                          0.8ex;border-left:1px solid
                          rgb(204,204,204);padding-left:1ex">Hello. I
                          have just subscribed to this list with this
                          address after being <br>
                          a long time lurker using my home email
                          address.<br>
                          <br>
                          I am looking for technical assistance after a
                          not quite successful <br>
                          recent Debian upgrade (from stretch to
                          buster). Is it appropriate for me <br>
                          to do so here? My Linux knowledge is still
                          pretty limited and I have not <br>
                          been able to find a solution to the problem
                          through extensive searches <br>
                          on the internet.<br>
                          <br>
                          If that is a reasonable request, I will detail
                          the problem, and what I <br>
                          have tried to do to fix it, in a separate
                          email.<br>
                          <br>
                          Thanks in advance.<br>
                          <br>
                          Joe Aquilina<br>
                          <br>
                          -- <br>
                          Joe Aquilina<br>
                          Central Chemical Consulting Pty Ltd<br>
                          PO Box 2546 Malaga WA 6944 Australia<br>
                          1/11 Narloo St Malaga 6090 Australia<br>
                          Tel: +61  8 9248 2739  Fax: +61  8 9248 2749<br>
                          <a href="mailto:joe@chem.com.au"
                            rel="noreferrer noreferrer" target="_blank"
                            moz-do-not-send="true">joe@chem.com.au</a> 
                          <a href="http://www.chem.com.au"
                            rel="noreferrer noreferrer noreferrer"
                            target="_blank" moz-do-not-send="true">www.chem.com.au</a><br>
                          <br>
_______________________________________________<br>
                          PLUG discussion list: <a
                            href="mailto:plug@plug.org.au"
                            rel="noreferrer noreferrer" target="_blank"
                            moz-do-not-send="true">plug@plug.org.au</a><br>
                          <a
                            href="http://lists.plug.org.au/mailman/listinfo/plug"
                            rel="noreferrer noreferrer noreferrer"
                            target="_blank" moz-do-not-send="true">http://lists.plug.org.au/mailman/listinfo/plug</a><br>
                          Committee e-mail: <a
                            href="mailto:committee@plug.org.au"
                            rel="noreferrer noreferrer" target="_blank"
                            moz-do-not-send="true">committee@plug.org.au</a><br>
                          PLUG Membership: <a
                            href="http://www.plug.org.au/membership"
                            rel="noreferrer noreferrer noreferrer"
                            target="_blank" moz-do-not-send="true">http://www.plug.org.au/membership</a><br>
                        </blockquote>
                      </div>
                    </blockquote>
                    <p><br>
                    </p>
                    <pre cols="72">-- 
Joe Aquilina
Central Chemical Consulting Pty Ltd
PO Box 2546 Malaga WA 6944 Australia
1/11 Narloo St Malaga 6090 Australia
Tel: +61  8 9248 2739  Fax: +61  8 9248 2749
<a href="mailto:joe@chem.com.au" rel="noreferrer noreferrer" target="_blank" moz-do-not-send="true">joe@chem.com.au</a>  <a href="http://www.chem.com.au" rel="noreferrer noreferrer" target="_blank" moz-do-not-send="true">www.chem.com.au</a></pre>
                  </div>
                  _______________________________________________<br>
                  PLUG discussion list: <a
                    href="mailto:plug@plug.org.au" rel="noreferrer
                    noreferrer" target="_blank" moz-do-not-send="true">plug@plug.org.au</a><br>
                  <a
                    href="http://lists.plug.org.au/mailman/listinfo/plug"
                    rel="noreferrer noreferrer noreferrer"
                    target="_blank" moz-do-not-send="true">http://lists.plug.org.au/mailman/listinfo/plug</a><br>
                  Committee e-mail: <a
                    href="mailto:committee@plug.org.au" rel="noreferrer
                    noreferrer" target="_blank" moz-do-not-send="true">committee@plug.org.au</a><br>
                  PLUG Membership: <a
                    href="http://www.plug.org.au/membership"
                    rel="noreferrer noreferrer noreferrer"
                    target="_blank" moz-do-not-send="true">http://www.plug.org.au/membership</a></blockquote>
              </div>
            </blockquote>
            <p><br>
            </p>
            <pre cols="72">-- 
Joe Aquilina
Central Chemical Consulting Pty Ltd
PO Box 2546 Malaga WA 6944 Australia
1/11 Narloo St Malaga 6090 Australia
Tel: +61  8 9248 2739  Fax: +61  8 9248 2749
<a href="mailto:joe@chem.com.au" target="_blank" rel="noreferrer" moz-do-not-send="true">joe@chem.com.au</a>  <a href="http://www.chem.com.au" target="_blank" rel="noreferrer" moz-do-not-send="true">www.chem.com.au</a></pre>
          </div>
          _______________________________________________<br>
          PLUG discussion list: <a href="mailto:plug@plug.org.au"
            target="_blank" rel="noreferrer" moz-do-not-send="true">plug@plug.org.au</a><br>
          <a href="http://lists.plug.org.au/mailman/listinfo/plug"
            rel="noreferrer noreferrer" target="_blank"
            moz-do-not-send="true">http://lists.plug.org.au/mailman/listinfo/plug</a><br>
          Committee e-mail: <a href="mailto:committee@plug.org.au"
            target="_blank" rel="noreferrer" moz-do-not-send="true">committee@plug.org.au</a><br>
          PLUG Membership: <a href="http://www.plug.org.au/membership"
            rel="noreferrer noreferrer" target="_blank"
            moz-do-not-send="true">http://www.plug.org.au/membership</a></blockquote>
      </div>
    </blockquote>
    <p><br>
    </p>
    <pre class="moz-signature" cols="72">-- 
Joe Aquilina
Central Chemical Consulting Pty Ltd
PO Box 2546 Malaga WA 6944 Australia
1/11 Narloo St Malaga 6090 Australia
Tel: +61  8 9248 2739  Fax: +61  8 9248 2749
<a class="moz-txt-link-abbreviated" href="mailto:joe@chem.com.au">joe@chem.com.au</a>  <a class="moz-txt-link-abbreviated" href="http://www.chem.com.au">www.chem.com.au</a></pre>
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