Questions[freesshd](server)

I'm experiencing sporadic problems when trying to ssh to windows servers (running either freesshd or Win32-OpenSSH, same results). When trying to run non-interactive commands (from Debian Jessie with OpenSSH client), sometimes (but not always, and at different intervals) remote command will stop and require pressing ENTER to continue.

For example:

ssh -4 -T somehost "mysqldump --master-data --all-databases" > backup.sql &

on some windows machines it finishes ok (if the databases are small enough) but on bigger ones it will usually stop (either immediately, with backup.sql remaining with size 0, or after some time, with backup.sql having from few megabytes to few hundred megabytes) and then shell will inform me that ssh client process is waiting for input:

[1]+  Stopped                 ssh -4 -T somehost "cat mysqldump --master-data --all-databases" > backup.sql

if I bring it to fg and press ENTER, it will continue working, even after I CTRL+Z and bg it. Sometimes it will finish then, other times it will stop again after some time.

strace confirms the process is waiting for TTY input (on file descriptor 4, which is RW opened /dev/pts/2 or similar PTY of shell spawning the ssh client) and that it is why process has been stopped.

If I run ssh from script without associated TTY it will die (as there is nobody to press ENTER). If I provide -n option to redirect stdin from /dev/null, ssh will die immediately upon connection. That poses additional problem, as ssh connections which are not run from terminal (but for example from cron(8)/atd(8)) will fail immediately.

Only close question I've found is this one, but the provided workaround (forcing PTY use) is not really applicable to my case (programs in question modify their behaviour when PTY is detected, adding ANSI sequencing and word wrapping etc).

Needless to say, the same commands that connect to hundreds of Debian (and other GNU/Linux) systems running OpenSSHD servers experience no problems whatsoever (weather using -n or not). Problems only ever arise when sshd server is running on microsoft windows.

Does anyone have ideas how to fix or work around the problem? I've tried naive approach of:

yes '' | ssh -4 -T somehost "mysqldump --master-data --all-databases" > backup.sql &

but it does not work well (while it fixes the ssh waiting for keyboard, it also randomly manages to insert newlines into output, which is unacceptable). Also related OpenSSH server on Windows refusing to work without STDIN even in noninteractive mode

I run an Openssh sshd service from Cygwin. When an RSA connection is established:

$ ssh Administrator@ZETA

Last login: Wed May 11 13:58:50 2016 from 10.1.1.140

-- there is no error message.

However, when I use an inline command:

$ ssh Administrator@ZETA "echo hi"

hi

-- the command works, but on ZETA the Windows Event Log now says:

sshd: PID 7068: error: get_socket_address: getnameinfo 2 failed: Unknown error

Calling this often fills the Event Log with errors.

Starting sshd on command line in debug mode:

 /usr/sbin/sshd -ddd

-- produces no error. It also runs under different user and I had to chown administrator /var/empty for it to work.

Trying to start sshd in debug mode as Windows service, as recommended in https://cygwin.com/ml/cygwin/2014-03/msg00488.html fails:

$ /usr/bin/cygrunsrv -I sshd -d "CYGWIN sshd_debug" -p /usr/sbin/sshd -a "-D -d -d -d" -y tcpip

/usr/bin/cygrunsrv: Error installing a service: OpenService: Win32 error 1073: The specified service already exists.

FreeSSHd is installed on Windows Server 2003, not on the C: drive but on another drive, D:. When I command-prompt to the D: drive and type in ssh, it tells me ssh is not recognised.

I added myself as a user to FreeSSHd with a hashed password and enabled SSH.

The Windows Firewall service is not running.

I can connect to the server using Remote Desktop Connection. I want to use ssh with Mercurial source code management system.

While I am logged onto the server via Remote Desktop connection, I can also connect to the server via ssh and putty on the client machine.

As soon as I log off from the server via Remote Desktop Connection, and I type in on the client:

ssh <username>@<server>

I get:

ssh: Connect to host <server> port 22: Connection refused

I am testing out running an SSH server on a local Windows VM.

I have installed FreeSSHd and set the command shell to "c:\cygwin\bin\sh --login -i" (bash as well) with "Use new console engine" unchecked. (When it was enabled no output would show through the ssh connection anyway)

The shell seems to work, but when connecting from my OS-X terminal using ssh all of the shell results comes out ill formatted.

      $ ls -al
          total 17
                  drwxr-xr-x+ 1 SYSTEM        Administrators 4096 Feb  2 01:00 .
drwxrwxrwt+ 1 Administrator Administrators    0 Feb  2 01:01 ..
                                                               -rw-------  1 SYSTEM        Administrators  128 Feb  2 01:30 .bash_history
                                                         -rwxr-xr-x  1 SYSTEM        Administrators 1150 Feb  2 00:55 .bash_profile
                                                   -rwxr-xr-x  1 SYSTEM        Administrators 3754 Feb  2 00:55 .bashrc
                                       -rwxr-xr-x  1 SYSTEM        Administrators 1461 Feb  2 00:55 .inputrc

Any ideas on why this is happening, how I can fix this?

I'm having an odd problem where FreeSSHD doesn't start on boot about one in ten times.

I'm using it on Amazon EC2 instances actually, since there's a bug in Amazon's version of Xen which makes it impossible to use cygwin/openssh on their 64-bit instances.

So if I take one image of Windows Server 2008 Data Center with FreeSSHD installed and set to run automatically as a service, and spin up 40 instances, FreeSSHd doesn't start on around 4 of them. The service isn't started and there's nothing in the sshd log file.

In the Event Log I see:

A timeout was reached (30000 milliseconds) while waiting for the FreeSSHDService service to connect. The FreeSSHDService service failed to start due to the following error: The service did not respond to the start or control request in a timely fashion.

But there's nothing else wrong, it seems to just be intermittent. If I remote desktop in and start the service manually later, it runs fine.

Any tips here on how to mitigate this? I'm trying to automate provisioning of these systems, so I really need sshd to start reliably without manual intervention.

FreeSSHD isn't really maintained any more, so I suspect I need a more generic Windows answer to this. Increase the timeout? Is there a way to get it to try again?