Re: sshd issues on Windows 10 version 1803

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

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On Jun 25 14:10, Corinna Vinschen wrote:
> On Jun 22 11:27, Hiya Z wrote:
> > Hello,
> > 
> > Now that Microsoft has bundled OpenSSH for Windows in update 1803 (see
> > https://blogs.msdn.microsoft.com/commandline/2018/03/07/windows10v1803/),
> > here are some observations and the resulting unfortunate behavior:
> > 
> > -  On a clean vanilla 1803 install, even with Windows Subsystem for Linux
> > (WSL) not installed, there exists a folder %SystemRoot%\system32\openssh
> > that has native Windows ssh and sshd executables.
> > 
> > -  %SystemRoot%\system32\openssh is added to the system PATH.
> > 
> > -  a (manual start) service "sshd", displayname="OpenSSH SSH Server",
> > imagepath=%SystemRoot%\system32\openssh\sshd.exe, gets created.
> > 
> > All of the above have the unfortunate consequence that Cygwin sshd no
> > longer works reliably on a 1803 install. First, the service name "sshd"
> > conflicts. This can be worked around by something like "ssh-host-config -N
> > cygwinsshd". Even then, the Cygwin sshd does not always automatically start
> > upon reboot. The Windows sshd is not configured/running, so there should
> > not be a port conflict. SCM reports timeouts (waiting for cygwinsshd to
> > respond) in the event viewer. A manual "sc start cygwinsshd" works, but
> > again, upon the next reboot, the problem is back.
> > 
> > There are other permutations depending on the sequence of install. If I
> > were to upgrade a Windows 10 1709 node with a working Cygwin sshd, it seems
> > that the 1803 update detects an existing sshd registry key (which really is
> > Cygwin), does not clobber the registry keys, nor does it install sshd.exe
> > under %SystemRoot%\system32\openssh (though ssh.exe and family get
> > installed). Even on this node, the Cygwin sshd shows the same issue of not
> > autostarting reliably upon reboots.
> > 
> > I am not sure what Cygwin can do... but reporting this issue to see if
> > Cygwin sshd can be fixed to autostart reliably upon reboots. As a minimum,
> > the default service name in ssh-host-config should be changed to not
> > collide with Windows "sshd".
> 
> There's also the problem that %SystemRoot%\System32\OpenSSH is now in
> %Path% by default.  Very nice of MIcrosoft to just overload the service
> name used by Cygwin for ages :(

However, the longer I think about it, the less I see the problem.  You
can run only one sshd service on port 22 anyway.  If you install 1803 on
a machine with Cygwin sshd service installed, the Microsoft service will
not override (which is rather courteous).  If you install a new machine,
Microsoft's sshd gets installed by default (nice), and if you want to
install Cygwin's sshd instead, you can simply remove the MSFT service
beforehand with `cygrunsrv -R sshd' (easy).


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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