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Bug 726839

Summary: Serial connection is broken after serial ports are detected
Product: Red Hat Enterprise Linux 6 Reporter: David Kovalsky <dkovalsk>
Component: kernelAssignee: Prarit Bhargava <prarit>
Status: CLOSED NOTABUG QA Contact: Red Hat Kernel QE team <kernel-qe>
Severity: high Docs Contact:
Priority: high    
Version: 6.1CC: arozansk, benl, peterm, prc
Target Milestone: rcKeywords: Regression
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2011-11-11 20:02:54 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description David Kovalsky 2011-07-29 22:19:05 UTC
In RHEL5, I was used to adding console=ttyS0 to grub.conf (and removing rhdb and quiet) which allowed me to see all kernel, later boot messages and in the end the login prompt appeared. 

This got broken in RHEL6. 

grub config:
default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
serial --unit=0 --speed=9600 --word=8 --parity=no --stop=1
terminal --timeout=5 console serial
hiddenmenu
title RHEL6 (2.6.32-171.el6.x86_64)
        root (hd0,0)
        kernel /vmlinuz-2.6.32-171.el6.x86_64 ro root=/dev/mapper/penny-rhel6 rd_LVM_LV=penny/rhel6 rd_NO_LUKS rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us nomodeset crashkernel=auto console=tty0 console=ttyS0,9600n1

I've made no other changes in /etc/init / /etc/sysconfig/init


Now when I boot, I see kernel messages all the way up to
...
ERST: Table is not found!
Non-volatile memory driver v1.3
Linux agpgart interface v0.103
crash memory driver: version 1.1
Serial: 8250/16550 driver, 4 ports, IRQ sharing enabled

And here the output stops. I can wait forever, but nothing appears.

I also have a VGA monitor connected, where the output keeps going. 

To get to the serial console prompt, I need to reset/restart the modem. Which sucks for 2 reasons:
 - the immediate output is lost. In case the system hangs during the boot before the console is restarted I'm not going to see it
 - the reconnecting itself is not very user friendly


Is it possible to get the same behaviour as in RHEL5?

[root@penny ~]# rpm -q upstart kernel util-linux-ng
upstart-0.6.5-10.el6.x86_64
kernel-2.6.32-171.el6.x86_64
util-linux-ng-2.17.2-12.el6.x86_64

Comment 2 Prarit Bhargava 2011-08-05 13:59:30 UTC
David, what type of system is this?

P.

Comment 3 David Kovalsky 2011-08-05 14:18:27 UTC
Hey Prarit, 

it's an older user grade AMD system with ASUS mobo.

What kind of info are you interested in? Will lspcie + dmidecode give you enough info?

Comment 4 Prarit Bhargava 2011-08-10 18:41:24 UTC
Try console=ttyS0,9600n81 .

P.

Comment 5 David Kovalsky 2011-10-05 12:18:41 UTC
Hi Prarit, 

it seems it's not actually a problem on the server side, but on the client side - issue in the cheap USB <--> serial converter. Because if I connect directly via serial <--> serial it works fine. 


And JFTR -  console=ttyS0,9600n81 makes no difference in my case.