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Old 12-28-2005, 11:22 AM   #1
Registered: Aug 2003
Posts: 36

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cat /dev/ttyS0: Input/output error

I am trying to setup heartbeat for high-availibility between two SuSE SLES9 linux servers. I need serial communication between two hp-dl360 machines via the serial port. I use a null-modem cable to do this.
The serial device on one of my systems gives me an error when i just do a simple
cat /dev/ttyS0. The error is below ,

mymachine-p:~ # cat /dev/ttyS0
cat: /dev/ttyS0: Input/output error

This happens on all the serial devices, /dev/ttyS0,ttyS1,ttyS2 etc

I have another SuSE linux box which has the exact same kernel/OS level, which has NO problems at all.

The linux version is as follows.
#uname -a
Linux mymachine-p 2.6.5-7.201-bigsmp #1 SMP Thu Aug 25 06:20:45 UTC 2005 i686 i686 i386 GNU/Linux

I have checked the BIOS settings, the serial ports are enabled , no problems at all.

Setserial command gives no error at all, see below

mymachine-p:~ # setserial -a /dev/ttyS0
/dev/ttyS0, Line 0, UART: 16550A, Port: 0x03f8, IRQ: 4
Baud_base: 115200, close_delay: 500, divisor: 0
closing_wait: 30000
Flags: spd_normal skip_test

Also, going a step ahead i removed the device and recreated it with mknod ,

mknod /dev/ttyS0 c 4 64 , and made sure it had the right permissions and the owner ship with uucp . Matched it exactly with the other working machine.

My SuSE SLES9 is patched and current.
mymachine-p:~ # less /etc/SuSE-release
SUSE LINUX Enterprise Server 9 (i586)

I am running out of ideas here , What do i do ? where do i look ?
I donot want to use my spare network port to do this, i need serial to be working,

Any pointers are greatly appreciated ,
Old 12-29-2005, 09:17 AM   #2
LQ Newbie
Registered: Dec 2005
Posts: 1

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Try the following like root

#cd /dev
#chmod 777 ttyS0

and all others devices that you want use


Old 12-30-2005, 12:48 PM   #3
Registered: Aug 2003
Posts: 36

Original Poster
Rep: Reputation: 15
I tried changing the permissions no luck at all.
Old 01-07-2006, 12:16 AM   #4
Registered: Jul 2004
Distribution: Blag
Posts: 35

Rep: Reputation: 15
I have the exact same problem on Debian sarge. I'm also trying to make a heartbeat cluster and I am unfortunately stuck at getting the serial connection working.

Does anyone have any ideas?


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