Thanks @Holger Parplies (wbppc AT parplies DOT de) for your reply.  See below:

-----Original Message-----
From: Holger Parplies [mailto:wbppc AT parplies DOT de]
Sent: Tuesday, May 30, 2017 3:31 PM
To: Akibu Flash <akibuflash AT outlook DOT com>
Cc: General list for user discussion, questions and support <backuppc-users AT lists.sourceforge DOT net>
Subject: Re: [BackupPC-users] Unexplained Error Code 255 - BackupPC

Hi,

Akibu Flash wrote on 2017-05-29 05:27:04 +0000 [Re: [BackupPC-users] Unexplained Error Code 255 - BackupPC]:
> [...]
> I am running backuppc version 4.41 on a Debian computer.

wow ... where did you get that version from?

        - I must have been asleep when I wrote version 4.4.1.  I meant version 4.1.1.


> When I start a backup, it appears to properly connect to my Windows
> computer and then gives me an error message.  ?Got fatal error during
> xfer (rsync error: error in rsync protocol data stream (code 12) at
> io.c(629) [Receiver=3.0.9.6])? [...] Please note that I am able to ssh
> and rsync into the Windows computer manually from the linux computer
                                      ^^^^^^^^
> without problem.

Also without extraenous output? You seem to be using rsync over ssh, and rsync is quite fussy about messages that it does not expect. As a rule of thumb, to a *Linux* computer,

   % ssh clientcomputer true
   %

should immediately display the next prompt as indicated above, i.e. nothing extra, not even blanks or newlines. For Windoze, your mileage may vary, but it probably won't. The actual invokation used by BackupPC (or rather rsync_bpc) might include extra options to ssh, e.g. -q -x -l someuser ... include those when testing.

        - Correct, Holger.  I am using rsync over ssh and ssh seems to work without a problem.  When I run the test you suggested:  "$ssh targetcomputer true", I merely get the prompt in response "$".  Strace seems to confirm that ssh is working correctly as when I ssh into the targetcomputer from the command line, and while running running strace on the targetcomputer, all seems to work as expected.  In addition, when I rsync into the targetcomputer from the command line, rsync appears to work just fine.

However, when I use the backuppc program to rsync into the very same targetcomputer, I get the Unexplained Error Code 255 message.  Below shows the ssh strace when I started a manual backuppc backup of some files on the targetcomputer, if that helps.  My log level is up to 9, but not much information is being generated.  I am unclear of how to diagnose as I am not that versed in linux.  Any help would be appreciated.   Thanks.  Akibu.

Strace command used:  $sudo strace -f -v -e open /etc/init.d/ssh restart

strace: Process 11860 attached
[pid 11860] open("/proc/self/oom_score_adj", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 10
[pid 11860] open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libcrypto.so.1.0.0", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libutil.so.1", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libz.so.1", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libcrypt.so.1", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/dev/null", O_RDWR)   = 3
[pid 11860] open("/proc/11860/fd", O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC) = 3
[pid 11860] open("/dev/urandom", O_RDONLY|O_NOCTTY|O_NONBLOCK) = 3
[pid 11860] open("/etc/gai.conf", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/etc/nsswitch.conf", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libnss_compat.so.2", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libnsl.so.1", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libnss_nis.so.2", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/lib/x86_64-linux-gnu/libnss_files.so.2", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/etc/passwd", O_RDONLY|O_CLOEXEC) = 3
[pid 11860] open("/usr/local/etc/ssh_host_rsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_rsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_rsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_rsa_key.pub", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_dsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_dsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_dsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_dsa_key.pub", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ecdsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ecdsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ecdsa_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ecdsa_key.pub", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ed25519_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ed25519_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ed25519_key", O_RDONLY) = 3
[pid 11860] open("/usr/local/etc/ssh_host_ed25519_key.pub", O_RDONLY) = 3
[pid 11860] open("/dev/tty", O_RDONLY|O_NOCTTY) = -1 ENOTTY (Inappropriate ioctl for device)
[pid 11860] open("/dev/null", O_RDWR)   = 4
strace: Process 11861 attached
[pid 11861] open("/dev/urandom", O_RDONLY|O_NOCTTY|O_NONBLOCK) = 6
[pid 11861] +++ exited with 255 +++
[pid 11860] open("/etc/localtime", O_RDONLY|O_CLOEXEC) = 4
[pid 11860] +++ exited with 255 +++
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=11860, si_uid=0, si_status=255, si_utime=0, si_stime=0} ---

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