[CentOS] Re: CentOS-5 Need Help With Serial Ports

[Stephen John Smoogen]

On Dec 21, 2007 1:38 PM, James B. Byrne <byrnejb at harte-lyne.ca> wrote:
> Taking a suggestion from the discussion regarding the aforementioned bug I
> altered /boot/grub/grub.conf and added this entry:
>
> title CentOS (2.6.18-53.1.4.el5xen-com1)
>         root (hd0,0)
>         kernel /xen.gz-2.6.18-53.1.4.el5 com1=38400,8n1
>         module /vmlinuz-2.6.18-53.1.4.el5xen ro
> root=/dev/VolGroup00/LogVol00 rhgb quiet xencons=xvc console=xvc
>         module /initrd-2.6.18-53.1.4.el5xen.img
>
>
> Which explicitly sets the console for the xen root to com1 and bypasses
> the module altogether.  This works as can be seen by:
>
> # setserial -g /dev/ttyS*
> /dev/ttyS0, UART: unknown, Port: 0x03f8, IRQ: 4
> /dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3
> /dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
> /dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
>
> However, since this fix will get clobbered on the very next kernel update
> the recommended method seems to be to add these rules to udev:
>
> ACTION=="add", SUBSYSTEM=="pnp", RUN+="/bin/sh -c 'while read id; \
>  do /sbin/modprobe pnp:d$$id ; done < /sys/$devpath/id'"
>
> Can somebody tell me how to do that?  Where do I do this.  I have very
> little experience with this sort of thing.  As this bug is reported
> upstream and is more than a year old I have some difficulty understanding
> how it persists in CentOS-5.
>

If upstream does not fix it, CentOS does not fix it. Bug for bug
compatible. Also I am not sure it is a true bug as much as an optional
system setting. Most of Xen documentation assumes your ttyS0 is being
run by Xen .. so turning it off from that way would be thought of
people as being bug who were going by the Xen docs.

-- 
Stephen J Smoogen. -- CSIRT/Linux System Administrator
How far that little candle throws his beams! So shines a good deed
in a naughty world. = Shakespeare. "The Merchant of Venice"