Carrier Detection in FreeBSD Post: 302821877

Sponsored Content

Operating Systems BSD Carrier Detection in FreeBSD Post 302821877 by rstor on Saturday 15th of June 2013 11:00:58 PM

06-16-2013

Registered User

My question was that according to my understanding of the documentation found here:

(27.4.6.1. Checking Out the FreeBSD System)
27.4.�Dial-in Service

When FreeBSD sees no carrier, getty should not have completed its open on the communications port. According to the setup described in my opening post, getty was opening the communications port regardless of carrier when the system is brought up. However; once there is a carrier signal applied, then it behaves correctly to my understanding.

I have found out where my problem was. Here is what I did:

I took two DB9 Male-Female connectors and removed all pins except receive, transmit, and ground. I connected the two connectors to each end of my null modem cable. The end result is a null modem cable that will only use these three lines.

I installed FreeBSD on an actual machine with a serial port (instead of using FreeBSD on VM Virtual Box with a usb-serial dongle). I connected my modified null modem cable to the FreeBSD machine and the other end to a PC.

Executing ps -ax on the above FreeBSD machine resulted in the following:

Code:

749 ?? S 0:00.01 /usr/libexxec/getty std.300 ttyu0

This is the correct behaviour to my understanding.

Using the modified cable on the virtual FreeBSD machine connected to a PC and executing ps -ax resulted in the following:

Code:

683 u0 Ss+ 0:00.06 /usr/libexec/getty std.300 ttyu0

Conclusion:

On the virtual FreeBSD machine which had a usb serial dongle, getty opens the communication port on system startup which it should not do to my understanding. On a real system it performs as indicated in the documentation.

rstor

View Public Profile for rstor

Find all posts by rstor

8 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

no carrier

I'm getting a error le0: No Carrier - transceiver cable problem? Tried looking around to see what is the best way to fix this error. Can anyone help me I can't find anything.

2. UNIX for Dummies Questions & Answers

virus detection

IS there virus software for unix? I worked in a Solaris environment and dont remember having anything. I also ask because the current enviroment i am working on is Microsoft and they argue that they do not use unix because of virus detection. Any input would be greatly appreciated.

3. IP Networking

modem detection

How to get information that where is my modem configured in /dev. I have two modems configured in my device .. one is USB and other is PCI modem.. USB is detected as /dev/USB0. but how to see about PCI modem?

4. Programming

Application crashes in FreeBSD 7.1 while working ok in FreeBSD 6.3

Hello there, My mulithreaded application (which is too large to represent the source code here) is crashing after installing FreeBSD 7.1-RELEASE/amd64. It worked properly on others machines (Dual Cores with 4GB of RAM - FreeBSD 6.2-RELEASE/i386). The current machine has 2x Core 2 Duo...

5. Shell Programming and Scripting

NAT detection

hellou, can anybody help me with nat detection in real time ? i prefer some detection script because i try some nat detection program's for example p0f or i'm using tcpdump, but i would get contain of specific packet. Some ideas?

6. Programming

Parallel Processing Detection and Program Return Value Detection

Hey, for the purpose of a research project I need to know if a specific type of parallel processing is being utilized by any user-run programs. Is there a way to detect whether a program either returns a value to another program at the end of execution, or just utilizes any form of parallel...

7. UNIX for Dummies Questions & Answers

Power Line Carrier (PLC)

hi, i am going to know if i can use n.s for power line simulating? Best Regards,

8. Solaris

Carrier Detection in Solaris 8 for Dial in and Null Modem Connections

I am having troubles with carrier detection for dialing in via a modem or direct connection via a null modem connection under Solaris 8 (i.e. login session remains active after the modem disconnects). I tried two different dumb modems (which do not respond to AT commands) on the machine that I am...

LEARN ABOUT MOJAVE

systemd-getty-generator

SYSTEMD-GETTY-GENERATOR(8)                                    systemd-getty-generator                                   SYSTEMD-GETTY-GENERATOR(8)

NAME

       systemd-getty-generator - Generator for enabling getty instances on the console

SYNOPSIS

       /lib/systemd/system-generators/systemd-getty-generator

DESCRIPTION

       systemd-getty-generator is a generator that automatically instantiates serial-getty@.service on the kernel console(s), if they can function
       as ttys and are not provided by the virtual console subsystem. It will also instantiate serial-getty@.service instances for virtualizer
       consoles, if execution in a virtualized environment is detected. If execution in a container environment is detected, it will instead
       enable console-getty.service for /dev/console, and container-getty@.service instances for additional container pseudo TTYs as requested by
       the container manager (see Container Interface[1]). This should ensure that the user is shown a login prompt at the right place, regardless
       of which environment the system is started in. For example, it is sufficient to redirect the kernel console with a kernel command line
       argument such as console= to get both kernel messages and a getty prompt on a serial TTY. See kernel-parameters.txt[2] for more information
       on the console= kernel parameter.

       systemd-getty-generator implements systemd.generator(7).

       Further information about configuration of gettys can be found in systemd for Administrators, Part XVI: Gettys on Serial Consoles (and
       Elsewhere)[3].

SEE ALSO

       systemd(1), agetty(8)

NOTES

        1. Container
               Interface
           https://www.freedesktop.org/wiki/Software/systemd/ContainerInterface/

        2. kernel-parameters.txt
           https://www.kernel.org/doc/Documentation/admin-guide/kernel-parameters.txt

        3. systemd for Administrators, Part XVI: Gettys on Serial Consoles (and Elsewhere)
           http://0pointer.de/blog/projects/serial-console.html

systemd 237                                                                                                             SYSTEMD-GETTY-GENERATOR(8)