Hi All,
I'm seeing something which I would not believe could happen had I not
seen it for myself. It's intermittent and thus not easily repeatable.
On client, I ran: "ssh -i cert -x -T -oBatchMode=yes example.com
batchjob" and ssh exited cleanly, immediately, and displaying no
output. When I saw it, I repeated the command, with the same results, a
few times.
On example.com, cert.pub is installed in .ssh/authorized_keys. Batchjob
is executable and in PATH, and starts (after #! /bin/sh) with "echo
"`date`: $0 $*" >> /tmp/log". Nothing appeared /tmp/log for those
occassions when client's ssh exited cleanly, immediately and without
displaying output. Nothing appeared in /var/log/syslog to indicate that
something was awry.
The one clue that I can think of, if it is a clue, is that I have two
DNS A records published for example.com, one for the primary instance
and the other for a hot-backup. Both are virtual servers hosted on
different Linux servers. The primary is running and the hot-backup is
not. DRBD is used to keep the hot-backup synchronised with the
primary. The idea is that I can switch server roles without needing to
reconfigure client. My experience is that openssh tries all A records
in sequence until it connects and that this is a viable strategy.
I feel that openssh would print something if it was unable to get a
connection, and, that having got a connection, example.com would print
something to /tmp/log. For ssh to cleanly exit with nothing output and
nothing logged stumps me.
Example.com is x64 architecture running Ubuntu 16.04.5. It's reasonably
up-to-date except for openssh-server, which is 1:7.2p2-4ubuntu2.4.
Client is Raspberry Pi 3B+ running Raspbian 9.4. Openssh-client is
1:7.4p1-10+deb9u3.
Both machines have plenty of free memory.
It's uncommon for me to reach out for ideas, but I'm reaching out now.
Any ideas?
Thanks in advance.
David
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