From Linux syslog (i.e., /var/log/messages), we have found the following repeated messages:
- Dec 17 04:21:41 myserver init: Id "co" respawning too fast: disabled for 5 minutes
As usual, we have taken action to investigate it. Here is the report on what we have found.
The serial ports in Linux are named ttyS0, ttyS1, etc. The /dev directory has a special file for each port. Type "ls /dev/ttyS*" to see them. Just because there may be (for example) a ttyS1 file, doesn't necessarily mean that there exists a physical serial port there.
For our issue, it turns out to be:
- ttyS1 physical serial port is not present on our host myserer
- Using setserial command
- Using dmesg command
Output from setserial Command
[aroot@myserver oracle]# setserial /dev/ttyS0 /dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4 [aroot@myserver oracle]# setserial /dev/ttyS1 /dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
Output from dmesg Command
[root@myserver ~]# dmesg | grep tty serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A 00:05: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
Because ttyS1 is absent, that is why the following line in /etc/inittab is failing and causes the re-spawning:
- co:2345:respawn:/sbin/agetty 9600 ttyS1
- init: Id "co" respawning too fast: disabled for 5 minutes
- $su aroot
- #vi /etc/inittab
- Commenting or removing the line for co
- #init q
You can verify that inittab is re-read by Linux kernel from the following line:
- Dec 17 23:49:40 myserver init: Re-reading inittab
in Linux syslog.