Thanks for the info - my problems turned out to be due to a combination of a flaky cable and a poor understanding of the sequence of events that happens when agetty/init handles the tty. In particular, once the cable was working I was still confused because I thought agetty had "died" after I logged in, when in fact it just went away because that's what it was supposed to do, attaching the login process to the tty. Once I had exited, init correctly respawned agetty. It helps ease confusion if you don't try changing the baud rate and repeatedly starting agetty "manually" while there's still a login process attached to the tty. ;-) I just needed some sleep to let my neural pathways destabilize a bit so I could think outside my own mental box.
-----Original Message----- From: Karl O . Pinc [mailto:[EMAIL PROTECTED]] Sent: Friday, June 07, 2002 2:33 PM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: Serial console login / null modem? On 2002.06.06 11:33 "Furnish, Trever G" wrote: > I'm trying to get a working login on my serial port and I'm running into > a > problem that I initially thought was because of a mis-wired null-modem, > but > now I think it's because of something I've missed in my linux > configuration. > Help??? > > I've tried a commercially made null modem cable and two cables I wired > myself using two different pin-outs, all with exactly the same results. > I > can get the login from the server to show up in the terminal window of > the > client, but I can't get the text from the client to go back to the > server. > If I use terminal programs on both sides, then the "server" can send text > to > the terminal window on the client, but the client can't send text back. > > The thing that makes me believe its a configuration problem is (besides > having used three different cables now), if I flip the cable over, the > behavior of DOES NOT CHANGE. That is, I can still send from the server > to > the client but not the other way around. I would expect that if it were > a > wiring problem, then flipping the cable over would reverse the symptoms. > > I'm using a redhat 7.2 system as the server, with /dev/ttyS0. I haven't > changed any devices or other setups - this is just minicom on the server > side talking to hyperterminal on the client side. Minicom can send text > to > hyperterminal but hypertrm can't send back. The settings are 9600bps, > 8n1, > hardware flow control on both sides. > > Am I missing something? Is there some "allow bidirectional" setting I'm > missing somewhere or that the device file may be missing? I've seen it > for > printer ports in the bios but not for serial ports... The only thing to note is that the computer (linux) rather than the terminal (windows), should generally be configured to echo each character it receives back down the wire to the terminal. See "man stty", "crt". Before you really start mucking about, here's some things to try. Easiest thing would be to take a device/cable that's known to work, like an external modem and plug it in and see about talking to it with minicom. You can also do cat /dev/ttyS0 & to watch what ttyS0 is receiving, and echo "foo" > /dev/ttyS0 send directly to the tty. If you really have a working null modem you should be able to plug it into ttyS0 and ttyS1 and use cat and echo to send stuff back and forth. Might be simpliest to try to add soemthing like # The ttyS1 serial line has a modem on it, allow login and fax S1:2345:respawn:/sbin/mgetty ttyS1 To /etc/inittab and then just try using it. (Any serial device should be able to login.) You can always plug an external modem into it and then try calling them modem from the next desk, if you know you have a modem cable and such that works. There's a Serial-HOWTO at www.tldp.org, have you tried that? I've always found it simpler to understand what Windoze was doing if I used the old Windows 3.1 terminal program rather than Hyperterminal, which IMHO tries too hard to do the things it thinks you want. Serial is always a pain. Karl <[EMAIL PROTECTED]> _______________________________________________ Redhat-list mailing list [EMAIL PROTECTED] https://listman.redhat.com/mailman/listinfo/redhat-list
