Linux Serial HOWTO (part 2/2)

Linux Serial HOWTO (part 2/2)

Post by Greg Hankin » Fri, 24 Mar 1995 04:55:27

Archive-name: linux/howto/serial/part2
Last-modified: 11 Mar 95

---This is part 2/2---

  But, you asked...  Edit /etc/login.defs, and find the line that says
  CONSOLE.  Add the name of the serial device to it.  Say I have my
  terminal on ttyS1.  I would change the line:

       CONSOLE tty1:tty2:tty3:tty4:tty5:tty6:tty8


       CONSOLE tty1:tty2:tty3:tty4:tty5:tty6:tty8:ttyS1

  16.7.  it just locks up.  I have my terminal connected to my PC, but
  after I type in a login name,

  You probably don't have CLOCAL in your /etc/gettydefs entry for the
  terminal, and you're probably not using a full null modem cable.  You
  need CLOCAL.  CLOCAL tells Linux to ignore modem control signals.
  Here is what it should look like:

       # 38400 bps Dumb Terminal entry

       # 19200 bps Dumb Terminal entry

       # 9600 bps Dumb Terminal entry

  Next, kill the getty process so a new one will be spawned with the new

  16.8.  At high speeds, my modem looses data.

  If you are trying to run your modem at > 19200 bps, and you don't have
  16550A UARTs, you should upgrade them.  See section ``What are
  UARTs?'' about UARTs.

  16.9.  them configured.  On startup, Linux doesn't report the serial
  devices the way I have

  This is true.  Linux does not do any IRQ detection on startup, it only
  does serial device detection.  Thus, disregard what it says about the
  IRQ, because it's just assuming the standard IRQs.  This is done,
  because IRQ detection is unreliable, and can be fooled.

  So, even though I have my ttyS2 set at IRQ 5, I still see

       Jan 23 22:25:28 misfits vmunix: tty02 at 0x03e8 (irq = 4) is a 16550A

  You have to use setserial to tell Linux the IRQ you are using.

  16.10.  rz and/or sz don't work when I call my Linux box on my modem.

  If Linux looks for /dev/modem when you try to transfer files, look at
  /etc/profile, and /etc/csh.cshrc.  There are a bunch of aliases
  defined there on some distributions, most notably Slackware.  These
  aliases mess up the zmodem programs.  Take them out, or correct them.

  16.11.  My screen is printing funny looking characters.

  This happens on virtual consoles when you send binary data to your
  screen, or sometimes on serial connections.  The way to fix this is to
  type echo ^v^[c.  For the control-character-impaired, thats echo

  16.12.  getty or uugetty still doesn't work.

  There is a DEBUG option that comes with getty_ps.  Edit your config
  file /etc/conf.{uu}getty.ttySN and add DEBUG=NNN.  Where NNN is one of
  the following combination of numbers according to what you are trying
  to debug:

       D_OPT   001            option settings
       D_DEF   002            defaults file processing
       D_UTMP  004            utmp/wtmp processing
       D_INIT  010            line initialization (INIT)
       D_GTAB  020            gettytab file processing
       D_RUN   040            other runtime diagnostics
       D_RB    100            ringback debugging
       D_LOCK  200            uugetty lockfile processing
       D_SCH   400            schedule processing
       D_ALL   777            everything

  Setting DEBUG=010 is a good place to start.

  If you are running syslogd, debugging info will appear in your log
  files.  If you aren't running syslogd info will appear in
  /tmp/getty:ttySN for debugging getty and /tmp/uugetty:ttySN for
  uugetty.  Look at the debugging info and see what is going on.  Most
  likely, you will need to tune some of the parameters in your config
  file, and you may have to configure your modem differently, too.

  16.12.1.  Alternate versions of getty

  You might like these better:

  mgetty, a different version of getty, can also handle faxes.  It can
  be found on the Linux FTP sites.

  agetty, a simpler version of getty.  This version comes with most
  distributions.  If not, it should be on the Linux FTP sites.

  17.  Contributions

  There was no possible way to write this HOWTO alone.  Although a lot
  of the HOWTO is my writing, I have often rewritten contributions to
  maintain continuity in the writing style and flow.  Thanks to everyone
  who has contributed or commented, the list of people has gotten too
  long to list (somewhere over fifty).  Special thanks to Matt Welch for
  coordinating the LPD project (I suspect that's much like herding
  cats), Ted T'so for answering questions about the serial drivers, and
  to Kris Gleason who maintains getty_ps.


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