https://dominik.wombacher.cc/2022-03-02T00:00:00+01:002022-03-02T00:00:00+01:002022-03-02T00:00:00+01:00Dominik Wombachertag:dominik.wombacher.cc,2022-03-02:/posts/sshd_error_bind_to_port_failed_cannot_assign_requested_address.html

<!-- SPDX-FileCopyrightText: 2023 Dominik Wombacher <dominik@wombacher.cc> --> <!-- --> <!-- SPDX-License-Identifier: CC-BY-SA-4.0 --> <p>I faced a very weird issue today, sshd failed to start on boot because <em>ListenAddress</em> was set but <em>network.target</em> doesn't mean IP addresses are already assigned and ready. So ... <a class="read-more" href="/posts/sshd_error_bind_to_port_failed_cannot_assign_requested_address.html"> [read more]</a></p>

<!-- SPDX-FileCopyrightText: 2023 Dominik Wombacher <dominik@wombacher.cc> --> <!-- --> <!-- SPDX-License-Identifier: CC-BY-SA-4.0 --> <p>I faced a very weird issue today, sshd failed to start on boot because <em>ListenAddress</em> was set but <em>network.target</em> doesn't mean IP addresses are already assigned and ready. So the configured IP isn't available, therefore sshd can't bind a Port and failed with <em>fatal: Cannot bind any address</em>.</p> <p>I thought this can be fixed by adjusting the sshd systemd unit, everything I found online also pointed into that direction, for example a <a class="reference external" href="https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982950">Debian</a> (Archive: <a class="reference external" href="https://web.archive.org/web/20220302224510/https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982950">[1]</a>, <a class="reference external" href="https://archive.today/2022.03.02-224450/https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982950">[2]</a>) and <a class="reference external" href="https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/216847/">Ubuntu</a> (Archive: <a class="reference external" href="https://web.archive.org/web/20210901133033/https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/216847/">[1]</a>, <a class="reference external" href="https://archive.today/2022.03.02-224617/https://bugs.launchpad.net/ubuntu/+source/openssh/+bug/216847/">[2]</a>) Bug report.</p> <pre class="code text literal-block"> /etc/systemd/system/ssh.service.d/override.conf [Unit] After=network-online.target auditd.service </pre> <p>The above systemd override seem to be one of the popular solutions which works for a lot of people. Unfortunately none of the various After/Wants combinations worked in my case on Debian 11.</p> <p>I had to go with the workaround to allow system wide port binding to not (yet) assigned IP addresses by adjusting two sysctl values as described on <a class="reference external" href="https://serverfault.com/a/941426">serverfault</a> (Archive: <a class="reference external" href="https://web.archive.org/web/20220302224659/https://serverfault.com/questions/941421/servers-fail-to-bind-to-addresses-at-boot/941426">[1]</a>, <a class="reference external" href="https://archive.today/2022.03.02-224737/https://serverfault.com/questions/941421/servers-fail-to-bind-to-addresses-at-boot/941426%23941426">[2]</a>).</p> <pre class="code text literal-block"> net.ipv4.ip_nonlocal_bind=1 net.ipv6.ip_nonlocal_bind=1 </pre> <p>Probably not the most elegant solution but it's working and due to the fact that multiple IP addresses are assigned to the Server, I have to specify on which the SSH Daemon is listening and can't just let em bind to all.</p>