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Please remove your /dev/cu* devices !

On May 12, Brian C. White wrote
> The following message is a list of items to be completed for the upcoming
> releases of Debian GNU/Linux.  If something is missing, incorrect, or you want
> to take responsibility for one or more items, please send email to:
> Brian White <bcwhite@verisim.com>


> - Use ttyS* devices instead of cua* devices (???) [10]

To All Developers : 

on most systems you will still have /dev/cu* devices (cui* (isdn), cua*
(serial), you should not have others, except if you have special serial

you don't need them. please remove these devices, so we will find
packages still using these devices and can change them to use the
corrensponded tty* device.

note : current makedev can create and remove cu* devices. but it will
not remove the cu* devices during an install script, because that may
breake existing setup. new bootdisks and base do not have cu* devices,
but you can create them with "/dev/MAKEDEV serial-cu|isdn-cu|...".

regards, andreas

> Footnotes
> ~~~~~~~~~

> 10 - /dev/ttySxx devices are fully POSIX-compliant TTY devices.  If you are
>      only going to be using one set of tty devices, you should be using
>      /dev/ttySxx.
>      /dev/cuaXX devices are different from /dev/ttySXX in two ways --- first
>      of all, they will allow you to open the device even if CLOCAL is not set
>      and the O_NONBLOCK flag was not given to the open device.  This allows
>      programs that don't use the POSIX-mondated interface for opening
>      /dev/ttySxx devices to be able to use /dev/cuaXX to make outgoing phone
>      calls on their modem (cu stands for "callout", and is taken from SunOS).
>      The second way in which /dev/cuaXX differs from /dev/ttySXX is that if
>      they are used, they will trigger a simplistic kernel-based locking
>      scheme: If /dev/ttySXX is opened by one or more processes, then an
>      attempt to open /dev/cuaXX will return EAGAIN.  If /dev/cuaXX is opened
>      by one or more processes, then an attempt to open /dev/ttySXX will result
>      the open blocking until /dev/cuaXX is closed, and the carrier detect line
>      goes high.
>      While this will allow for simple lockouts between a user using a modem
>      for callout and a getty listening on the line for logins, it doesn't work
>      if you need to arbitrate between multiple programs wanting to do dialout
>      --- for example, users wanting to do dialout and UUCP.
>      I originally implemented the cuaXX/ttySXX lockout mechanism back before
>      FSSTND established a standard convention for the use of tty lock files.
>      Now that it's there, people should use the tty lock files and not try
>      using /dev/cuaXX.  The only reason why /dev/cuaXX hasn't disappeared yet
>      is for backwards compatibility reasons.
>                                 -- Theodore Ts'o <tytso@mit.edu>

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