I'd suggest using a udev rule that runs simple script to enable/disable your
tty.  All you'd need to do is match your modem in a udev rule and call a
script to change your inittab.

That way it only runs if/when the modem is plugged-in.

Cheers,
sV



On 29 March 2010 11:10, Tom Munro Glass <[email protected]> wrote:

> A client is deploying several CentOS machines to remote sites, some of
> these
> have broadband access but some use dial-up for remote administration. Part
> of
> the standard configuration is to install a USB modem driver and to add the
> following line to /etc/inittab:
>
> ACM0:2345:respawn:/sbin/mgetty -x 0 -n 6 -D ttyACM0
>
> to allow us to dial into the machine.
>
> This is fine *IF* the USB modem is physically installed and being used, but
> on
> sites using broadband where a modem is not usually installed
> /var/log/messages
> fills up with a large amount of the following:
>
> Mar 28 22:56:50 localhost mgetty[4828]: mod: cannot open line /dev/ttyACM0:
> Input/output error
> Mar 28 22:56:50 localhost mgetty[4828]: open device /dev/ttyACM0 failed:
> Input/output error
> Mar 28 22:56:50 localhost mgetty[4828]: cannot get terminal line
> dev=ttyACM0,
> exiting: Input/output error
> Mar 28 22:56:50 localhost init: Id "ACM0" respawning too fast: disabled for
> 5
> minutes
>
> Similar messages are also written to /var/log/mgetty.log.ttyACM0.
>
> You might think the obvious solution is to not set up the modem if it's not
> being used, but this isn't what the client wants. The CentOS machine is
> headless, and in the event of a broadband failure we need an engineer to be
> able to simply plug in a modem to give us remote access to it.
>
> So, is there some way of reducing the amount of messages ending up in the
> log
> files? I have already added '-x 0' to minimise output from mgetty but the
> messages shown above are still getting through.
>
> Tom Munro Glass
>
>

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