Folks
I just installed a centos6 system on a 64-bit box. My methods
include remote administration, using ssh from a windows machine. I
use this method successfully on several Centos5 boxes and one Centos6
(32bit) machine as well. However, on this latest one, I get
inconsistent results with ssh. This is a server, SELINUX is
disabled, it's command line only, and I have installed sendmail,
apache, vsftpd (but haven't used the last two yet). The machine is
connnected internally only (behind NAT), so is invisible to the outside world.
In a successful use of SSH just after installing the needed software,
I installed the DSA keys so no password is used. Subsequent to that,
and at seemingly unpredictable frequent attempts, I get results such as
a) A successful SSH login as desired. Variious commands, sucn as
"ls" and such, work fine.
b) A successful login, but a write failure with whatever I enter next
c) Connection refused
d) A request for password (followed by failure)
I can't seem to connect these various errors with any activity on the
server -- I'm monitoring /var/log/messages /var/log/secure and
/var/log/audit/audit.log, on a terminal directly attached to the server.
The server, and my windows box (which is my admin box) are on the
same internal IPV4 network (192.168.xxx.xxx), all controlled by a
Centos5 gateway running just fine which provides DHCP and NAT when needed.
I haven't been able to correlate these failures with anything I do;
there's no indication on the server that anything is happening. Of
course, when the SSH login succeeds, there's a notation in the logs,
but no evidence of the failures.
I tend to get "best" results after a bootstrap,
With no evidence of anything abnormal showing up in the logs, it's
not clear where to look. I would appreciate some clues as to where
to look next. The server seems to have functioning internet access
through the gateway. I can easily redo the install if needed. The
hardware was previously running Win7, so I suspect it's good
hardware. It's a roll-you-own machine built with components from
Fry's, so don't ask me for the model name :-)
I'd appreciate advice or guidance.
David Kurn
SOLUTION:
(with embarrassment)
It turns out that one of the Ethernet switches in the path was not
behaving properly. I removed it, and the problem disappeared. Sorry
to have raised a red-flag ... the problem has been bugging me for 5
days and only today did I look at the switch.
