[ale] locked serial port

Jim Lynch jwl at sgi.com
Wed Aug 25 16:09:06 EDT 1999

As an aside, the author of the serial port stuff a long time ago
suggested that you not use /dev/cua* ports any longer.  You should be
using the /dev/ttyS* ports.

Alan Bowman wrote:
> > I have a locked serial port that I cannot seem to unlock.  I've looked
> > in all the customary spots for locks: i.e. /var/lock and
> > /var/spool/uucp.  The Serial HOWTO talked about lock files in
> > /usr/spool/uucp but I don't have one of those.  I have tried deleting
> > the device and re-creating it.  I have shutdown and restarted.  I can't
> > seem to get anywhere.
>  Are the two machines still connected?  If so, the -other- machine may
> be where the locked port is.  Try this, on your end: go superuser, and
> at the #..
> # fuser -k /dev/cua1 <return> (the next line is the stout for fuser)
> /dev/cua1: some numbers here,representing PID's,and your prompt below
> # (you get your pound sign back)
> At the next #, run the fuser command again.  If the PID numbers stay the
> same, then the port is still locked. At this point the only thing that
> unlocks it is a power off shutdown. If it's still locked after that,
> then the next likely culprits are either a bad port(s)/cable(s).  If,
> however, the fuser command gives you a different set of PID's every
> time, then the port 'thinks' it is open.  fuser kills the process
> running on that port, and starts a new one.  In this case, it should
> start a new getty, since you're going for a login on a serial port.  If
> fuser doesn't give you login on the other machine, check cables and
> connections.  Also check the inittab.  I can't say for sure how the
> inittab is set up on RH, but it should have entries for all the consoles
> and the serial ports.
>   What kind of cable are you using?  I know that at work we have to
> change the crossover for the pins if the cable is going from the comm
> port on one PC to the comm port on another. This, though, is using RJ45
> modular adapters and Cat5 cable, not a standard serial cable.
> Unfortunatly, I can't remember off the top of my head just what pins
> they are.
>  > Can you suggest a way to unlock my /dev/cua1 port?
>   Well, there's one suggestion.  I'm sure someone more familiar with RH
> will have a better one.  I'm a Slackware kind of guy, but guess that the
> two distro's should behave fairly similarly.
> ...alan
> --
> --------------------------------------------------------------
> The very powerful and the very stupid have one thing in common.
> Instead of altering their views to fit the facts, they alter the facts
> to fit their views ... which can be very uncomfortable if you happen to
> be one of the facts that needs altering.
>        -- Doctor Who, "Face of Evil" (linux fortune)

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