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

James B. Byrne byrnejb at harte-lyne.ca
Fri Dec 21 20:38:47 UTC 2007


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.

Regards,

-- 
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