I'm experiencing the same problem with Ubuntu 16.04.5 on OpenVZ (with
kernel: 2.6.32-042stab127.2).
The workaround that I found is to edit `/usr/lib/tmpfiles.d/sshd.conf`
in the following way:
d /run/sshd 0755 root root
Here is the question on askubuntu.com, where my case decribed in more
details: https://askubuntu.com/q/1109934/566421
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https://bugs.launchpad.net/bugs/1811580
Title:
systemd fails to start sshd at reboot
Status in systemd package in Ubuntu:
Confirmed
Bug description:
Ubuntu 16.04.5, systemd 229-4ubuntu21.15
The latest systemd update has somehow changed the method it uses to
start 'ssh.service' i.e. 'sshd'. systemd fails to start sshd if
/etc/ssh/sshd_config contains "UsePrivilegeSeparation yes" and
/var/run/sshd/ does not already exist. Being as this is the default,
virtually EVERY Ubuntu 16.04 server in the world has
UsePrivilegeSeparation set to yes. Furthermore, at the time when the
user performs 'apt upgrade' and receives the newest version of
systemd, /var/run/sshd/ already exists, so sshd successfully reloads
for as long as the server doesn't get rebooted. BUT, as soon as the
server is rebooted for any reason, /var/run/sshd/ gets cleaned away,
and sshd fails to start, causing the remote user to be completely
locked out of his system. This is a MAJOR issue for millions of VPS
servers worldwide, as they are all about to get locked out of their
servers and potentially lose data. The next reboot is a ticking time
bomb waiting to spring. The bomb can be defused by implicitly setting
'UsePrivilegeSeparation no' in /etc/ssh/sshd_config, however
unsuspecting administrators are bound to be caught out by the
millions. I got caught by it in the middle of setting up a new server
yesterday, and it took a whole day to find the source.
The appropriate fix would be to ensure that systemd can successfully
'start ssh.service' even when 'UsePrivilegeSeparation yes' is set.
systemd needs to test that /var/run/sshd/ exists before starting sshd,
just as the init.d script for sshd does. openssl could also be patched
so that UsePrivilegeSeparation is no longer enabled by default,
however that is not going to solve the problem for millions of pre-
existing config files. Only an update to openssl to force-override
that flag to 'no' would solve the problem. Thus systemd still needs to
be responsible for ensuring that it inits sshd properly by ensuring
that /var/run/sshd/ exists before it sends the 'start' command.
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