[CentOS] how to rescan serial ports without reboot

Scott Silva ssilva at sgvwater.com
Wed Dec 3 16:16:55 UTC 2008

on 12-3-2008 6:30 AM Rudi Ahlers spake the following:
> Hi all,
> I hope this is possible. I have a server, with a network switch
> attached to the serial port, and I want to rescan the serial port
> (/dev/tty) to see if it picks it up? I'd prefer not to reboot the
> server if at all possible.
> dmesg reports ttyS0 as the active port:
> [root at zabackup01 ~]# dmesg |grep tty
> Bootdata ok (command line is ro root=/dev/System/root rhgb quiet xencons=tty6)
> Kernel command line: ro root=/dev/System/root rhgb quiet xencons=tty6
> WARNING: Failed to register Xen virtual console driver as 'tty1'
> serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> 00:06: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
> ttyS0: 1 input overrun(s)
> ttyS0: 1 input overrun(s)
> running screen /dev/ttyS0 doesn't show up anything, and I should at
> least get the switch's login prompt.
You shouldn't have to re-scan anything. If the serial port was there at boot,
it would have been detected. I hook up to routers that are headless all the
time and the serial ports work as expected. Nothing needs to be connected to
it for it to be seen. If your switch isn't responding, maybe your port speed
is wrong or something, or your cable is wrong.

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