[CentOS] ssh session output stalls

[William L. Maltby]

On Sun, 2006-06-25 at 14:20 -0500, Larry Vaden wrote:
> Hello,
> 
> Is anyone else having problems with the ssh session output stalling
> when ssh'd to another system and the command is running via sudo and a
> pager is being used (e.g., more)?
> 
> Too highly reproducible :(  to date, all known occurrences have
> involved Centos 4.3 servers;  makes no difference whether client is
> RHEL WS 4.3, Centos 4.3 or FC 5 or WinDoze.  Makes no difference if
> terminal emulator is Gnome's stock issue or Konsole or Putty.  Not
> sure about SecureCRT.

If sudo is removed from the mix, does it still happen?

> 
> Sometimes one can break loose the logjam;  if so:
> . terminal prompts are stacked left to right vs. vertically
> . keyboard input is not echo'd

These two tell us that end-of-line and other terminal settings (usually
NL on *IX systems, but I don't know about ssh) are getting lost before
the pager is seeing them. Possibly doing stty against the pseudo-terms
involved will give a clue?

> . in this event, terminal clear/reset doesn't
> end if so.
> 
> Any thoughts?

Generally, having a pager involved when there are interactive prompts
("terminal prompts are stacked...") is a bad idea. Commands often issue
prompts with no EOL so that you see on one line something like

  Enter reply [Y/N/Q] -

and the cursor is after the dash. The pager usually works on *lines* not
*characters*, although some used to have timeouts that could be applied
to force output flushing (don't know if this applies anymore).

Wish I had more to offer than just a couple Qs that might get you going.


> 
> rgds/ldv
> 
> [vaden at mx1 ~]$ ps auxw | grep -i pts/0
> vaden     2475  0.0  0.1 37444 3064 ?        S    04:53   0:00 sshd: vaden at pts/0
> vaden     2476  0.0  0.0 53964 1480 pts/0    Ss   04:53   0:00 -bash
> root      2511  0.0  0.0 71284 1312 pts/0    S    04:53   0:00 su -
> root      2512  0.0  0.0 53968 1492 pts/0    S    04:53   0:00 -bash
> root      3426  0.0  0.0  2376  288 pts/0    S+   13:57   0:00 sesh
> /bin/grep -i unknown /var/log/maillog
> root      3427  0.1  0.0 51128  784 pts/0    S+   13:57   0:00
> /bin/grep -i unknown /var/log/maillog
> vaden     3434  0.0  0.0 51072  540 pts/1    R+   13:58   0:00 grep -i pts/0
> <snip sig stuff>

-- 
Bill
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