<div dir="ltr"><div>Hi Kevin,</div><div><br></div><div>Based on my understanding and a discussion with the SLURM dev team on that subject, here are some information about the new support of X11 in slurm-17.11 :</div><div><br></div><div>- slurm's native support of X11 forwarding is based on libssh2</div><div>- slurm's native support of X11 can be disabled at configure/compilation time using the --disable-x11 configure pragma</div><div>- slurm-spank-x11 can be used only if you disable slurm's native support of X11 at configure/compilation time</div><div><br></div><div>The simplest case with --pty available since 1.3 only works if you do not really want to secure your X11 forwarding (using xhost +...).</div><div><br></div><div>libssh2 yet offers a subset of the capabilities of openssh (less encryption methods, less authentication methods, ...). If you need options only available in openssh, you should use slurm-spank-x11 instead of slurm's native support of X11. That is what we are doing with 17.11 as we need GSSAPI support for kerberos authentication, a support that is not provided by libssh2 right now.</div><div><br></div><div>Take a look at <a href="https://www.libssh2.org/" target="_blank">https://www.libssh2.org/</a> to figure out if the provided features is sufficient for you. If it is the case, I guess that using slurm's native support of X11 will be easier than having to compile, install and configure slurm-spank-x11.</div><div><br></div><div>Looking at the code in current slurm-17.11 (src/slurmd/slurmstepd/x11_<wbr>forwarding.c), the logic behind slurm's native support of X11 differs from slurm-spank-x11 when it comes to establish the ssh connections required to secure the X11 forwarding. If my understandings are correct, native logic is to redirect a local port on the compute node to the X11 port on the submission/login node using libssh2 direct-tcpip channels (equivalent to -L %port:%host:%port in openssh) and set that local port as the X11_DISPLAY to use locally by the applications. Hostbased authentication and pubkey authentication are the two authentication logics that are tried. So you need to have either hostbased authentication configured on your cluster or pubkey/private keys available and configured for all of your users in their home directories, readable on the compute nodes after seteuid/setegid.</div><div><br></div><div><br></div><div>HTH.</div><div><br></div><div>Matthieu<br></div><div class="gmail_extra"><br><div class="gmail_quote">Le 29 nov. 2017 21:20, "Kevin Manalo" <<a href="mailto:kmanalo@jhu.edu" target="_blank">kmanalo@jhu.edu</a>> a écrit :<br type="attribution"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p><a name="m_3960324935357312669_m_-8037961477578061144_m_1728210410527644450_terminal" style="font-family:Calibri,sans-serif;font-size:12pt;color:rgb(33,33,33)"><span style="font-size:11pt;color:black;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background-image:initial;background-position:initial;background-size:initial;background-repeat:initial;background-origin:initial;background-clip:initial">Hello
SLURM users,</span></a><br>
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<p class="MsoNormal"><span><span style="font-size:11pt;color:black;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"> </span></span></p>
<p class="MsoNormal"><span><span style="font-size:11pt;color:black;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%">I was reviewing the X11 documentation</span></span></p>
<p class="MsoNormal"><span><span style="font-size:11pt;color:black;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"> </span></span></p>
<p class="MsoNormal"><span></span><a href="https://slurm.schedmd.com/faq.html#terminal" target="_blank"><span><span style="font-size:11pt;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%">https://slurm.schedmd.com/faq.<wbr>html#terminal</span></span><span></span></a><span><span style="font-size:11pt;color:black;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"></span></span></p>
<p class="MsoNormal"><span></span><a href="https://slurm.schedmd.com/faq.html#x11" target="_blank"><span><span style="font-size:11pt;border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%">https://slurm.schedmd.com/faq.<wbr>html#x11</span></span><span></span></a><span><span style="font-size:11pt;color:rgb(21,120,183);border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"></span></span></p>
<p class="MsoNormal"><span><b><span style="font-size:11pt;color:rgb(21,120,183);border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"> </span></b></span></p>
<p class="MsoNormal"><span><b><i><span style="font-size:11pt;color:rgb(21,120,183);border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%">15. Can tasks be launched with a remote terminal?</span></i></b></span><span></span><i><span style="font-size:11pt;color:rgb(70,84,92)"><br>
<span style="background:white none repeat scroll 0% 0%">In Slurm version 1.3 or higher, use srun's <span style="border-color:windowtext;border-style:none;border-width:1pt;padding:0in">--pty</span> option. Until then, you can accomplish this by starting an appropriate program or script. In the simplest case (X11
over TCP with the DISPLAY environment already set), executing <span style="border-color:windowtext;border-style:none;border-width:1pt;padding:0in">srun xterm
</span>may suffice.</span></span></i><b><i><span style="font-size:11pt;color:rgb(21,120,183);border-color:windowtext;border-style:none;border-width:1pt;padding:0in;background:white none repeat scroll 0% 0%"></span></i></b></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="font-size:11pt">At our site, indeed this is sufficient. We are using the <a href="https://github.com/hautreux/slurm-spank-x11" target="_blank">https://github.com/hautreux/s<wbr>lurm-spank-x11</a> plugin currently.</span></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="font-size:11pt">I see that in the 17.11.0 announcement</span></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<p class="MsoNormal"><i><span style="font-size:10pt;font-family:"Arial",sans-serif;color:rgb(34,34,34);background:white none repeat scroll 0% 0%"> -- X11 support is now fully integrated with the main Slurm code. </span></i><i><span style="font-size:10pt;font-family:"Arial",sans-serif;color:rgb(34,34,34)"><br>
<span style="background:white none repeat scroll 0% 0%">Remove any </span><br>
<span style="background:white none repeat scroll 0% 0%"> X11 plugin configured in your plugstack.conf file to avoid errors being </span><br>
<span style="background:white none repeat scroll 0% 0%"> logged about conflicting options. </span></span></i><i><span style="font-size:11pt"></span></i></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="font-size:11pt">Questions</span></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<ol start="1" style="margin-top:0in" type="1">
<li class="m_3960324935357312669gmail-m_-8037961477578061144m_1728210410527644450MsoListParagraph" style="margin-left:0in"><span style="font-size:11pt">If ‘srun —x11’ is not needed to X11 forward (the simplest case works), do we encourage users to use it? I’m more in need of understanding how it works because some users use
it, some do not, and more education on this would be great.</span></li><li class="m_3960324935357312669gmail-m_-8037961477578061144m_1728210410527644450MsoListParagraph" style="margin-left:0in"><span style="font-size:11pt">Is the SLURM spank x11 plugin now unnecessary once we build 17.11.0 with the updated configuration?</span></li></ol>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
<p class="MsoNormal"><span style="font-size:11pt">Thanks,</span></p>
<p class="MsoNormal"><span style="font-size:11pt">Kevin</span></p>
<p class="MsoNormal"><span style="font-size:11pt"> </span></p>
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