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Re: PPP Dialin + Dialout



On 26-Aug-98 Ira Abramov wrote:
> check out the serial howto, there's a reason why Linux is supplied with
> both ttyS? and cua? devices, I can never remember which is which, but one
This HOWTO contains some obsolete info. The cua? devices were meant to enable
only one process at a time to open the device ("Device Busy" for subsequent
processes). However, mgetty (as an example) need to keep the device open at all
times quitely for dial-in and at the same time let other processes (e.g: pppd)
dial-out. Therefore, we use the ttyS? devices for both (allowing multiple
processes to open the same device), but have the processes discipline the usage
via the good-old-uucp-file-locking-scheme.

In short - Always use ttyS? devices unless you really want single process to
use the device and block it for others (almost always not true). Use
application level locking instead (UUCP lock files).

----------------------------------------------------------------
Oron Peled                             Voice/Fax: +972-4-8228492
oron@actcom.co.il                  http://www.actcom.co.il/~oron

"To err is human, to really fuck things up takes root.... except on
Windows, where everyone is root."