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Operating Systems OS X (Apple) No terminal (tty) after ssh and telnet also Post 302374342 by Frank.Knobloch on Tuesday 24th of November 2009 07:12:49 AM
Old 11-24-2009
No terminal (tty) after ssh and telnet also

Hi all,

we are just confused about a strange problem on one server in production (XServer, running OSXS 10.5.6). It works normal for month. Since two day everthing seems to be fine also with one exception.

When we connect trough ssh we won't get a tty session. For testing purposes, we enabled telnet and try to connect from another server behind the firewall to the machine. But no "login" occured.

If you launch something like ssh user@machine "my command" you will get the output as normal.

We don't know the reason. Fact is, no system update oder software update was done since the last weeks and ssh worked properly till Saturday.

I think it's no problem of ssh. It's something behind ssh. But ssh -vvv won't give more information.

So our current workaround is ssh user@server "bash". But this is extremly uncomfortable without concrete ttys. Using this way and e.g. running vi will give the short information:

Code:
Vim: Warning: Output is not to a terminal
Vim: Warning: Input is not from a terminal

So this is also a hint, that ssh works, but something behind doesn't work. We don't find "interesting" things in message logs or so.

Any hints for further analyze?

Do anybody now which service or process will be responsible to return a "tty session" to ssh or telnet?


Frustrated but hopefull

Frank
 

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ZSSH(1) 							       ZSSH								   ZSSH(1)

NAME
zssh - interactive file transfer wrapper for ssh SYNOPSIS
zssh [zssh options] [--] [ssh options] ztelnet [zssh options] [--] [telnet options] DESCRIPTION
zssh (Zmodem SSH) is a program for interactively transferring files to a remote machine while using the secure shell ( ssh ). It is intended to be a convenient alternative to scp , allowing to transfer files without having to open another session and re-authenticate one- self. zssh is an interactive wrapper for ssh used to switch the ssh connection between the remote shell and file transfers. This is achieved by using another tty/pty pair between the user and the local ssh process to plug either the user's tty (remote shell mode) or another process (file transfer mode) on the ssh connection. ztelnet behaves similarly to zssh, except telnet is used instead of ssh. It is equivalent to 'zssh -s "telnet -8 -E"' Files are transferred through the zmodem protocol, using the rz and sz commands. zssh behaves as an usual ssh session until the escape sequence is depressed ( default is ^@ which can be produced by pressing C-space, or C-2, or C-` ), which enables file transfer mode. A new prompt is then displayed, and commands can be executed locally to initiate file transfers (among other things). It roughly behaves as a local shell featuring line edition, history and completion (thanks to libreadline), globbing, and escape characters ( " ' and ). The following builtins are handled by zssh itself: ? , cd , disconnect , escape , exit , help , hook , quit , repeat , rz , suspend , sz , version cd <dir> change current directory disconnect disconnect and exit escape [^X] Change escape key to ^X. Without argument, print current escape key exit exit file transfer mode. ^D may also be used for this purpose. help print help and tips ? hook prg [args] Hook program 'prg' on the the pty. Its standard input and output will go through the ssh channel. typing 'sz'/'rz' is in fact equivalent to 'hook sz'/'hook rz' A weird imagination is most useful to gain full advantage of this feature. quit same as exit. repeat repeats cmd forever (^C to interrupt). Useful for example if you use a remote script invoking "sz" and you don't want to be typing "rz" each time... Remember however that several files can be transferred by a single sz/rz pair so this is not usually necessary to use repeat. rz Receive files from the remote machine. runs rz and plugs the process on the ssh connection. running sz on the REMOTE machine is required : 1) run `sz <remote_file> ...' from the remote machine shell 2) press the escape sequence (C-space) to enter file transfer mode 3) run the `rz' builtin suspend suspend zssh (back to the local machine shell) sz <file> ... Send files to the remote machine. runs sz and plugs the process on the ssh connection. There is no need to manually run rz on the remote side. version print version information builtins rz , sz , hook and exit return to shell mode after completion. OPTIONS
-f --force Do not ask user any question -h --help show basic help -s cmd --shell cmd run cmd as remote shell instead of the default "ssh -e none" (zssh) or "telnet -8 -E" (ztelnet) ex: zssh -s "rsh -x" -V --version show version -z ^X --zssh-escape ^X set escape sequence to ^X -- may be used to separate zssh options from ssh ones Other arguments are passed verbatim to ssh/telnet/whatever. ENVIRONMENT
ZSSHESCAPE Setting the ZSSHESCAPE environment variable allows to override the default escape sequence. ZSSHESCAPE should contain only two characters of the form `^X', meaning that ^X is to be the new escape sequence. REQUIREMENTS
the following binaries need to be properly installed for zssh to work : ssh/telnet/... the remote shell to be executed (local machine) sz rz zmodem send and receive programs. Should be both on local and remote machine, and (hopefully) of compatible versions. TIPS
If file transfer is initiated but never completes ( ie a line like : Bytes Sent: 38144/4610624 BPS:3424 ETA 22:15 or Bytes Sent: 0/ 513 BPS:0 ETA 00:00 Retry 0: Got ZCAN can be seen, but transfer never completes ) Chances are the pty/tty on one of the systems are not 8-bit clean. (Linux is 8-bit clean, NetBSD is not). Using the -e (escape) option of rz should solve this problem. Transfers can be interrupted with ^C (somewhat experimental =) If you get stuck in rz/sz (for example you've just ran rz, but you then decided not to transmit anything), hit a dozen ^X (Ctrl-X, not the zssh escape!) to stop it Use `sz -y <files>' to overwrite files on the other side BUGS
/ LIMITATIONS You may sometimes have to hit return 2 or 3 times after file transfer completion in order get back to the shell. Some digits are usually displayed; don't worry it won't harm (you or your term) ... the tty may (sometimes) be somewhat upset after an interrupted transfer ( using ^C ). typing `reset' in this case should help. no pipe, redirection (and other stuff) support in shell ... but after all there are already wonderful shells around =) CREDITS
ttssh's author - Robert O'Callahan - for the original idea The sourceforge team. AUTHOR
Matthieu Lucotte <gounter@users.sourceforge.net> zssh homepage: http://zssh.sourceforge.net SEE ALSO
ssh(1), telnet(1), scp(1), sz(1), rz(1), readline(3), ZSSH
June 26, 2000 ZSSH(1)
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