HP Linux Server Management Software User Manual
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C Frequently Asked Questions and Troubleshooting
Information
This section contains frequently asked questions and the answers to those questions. Some of the questions
and answers supplied in this section provide troubleshooting information.
How does the Linux kernel order serial ports (UARTs)?
1.
HCDP (Headless Console and Debug Port) Console UART is the UART set in the EFI Console- In/Out
table. It will always be ttyS0 regardless of whether the operating system uses a serial console.
2.
ACPI Namespace UARTs are the built-in UARTs on HP Integrity systems. They are numbered in order
(i.e. 1, 2 or A, B).
Note: Port [1|A] may be selected for Console-In/Out, and would therefore be discovered as ttyS0.
3.
PCI UARTs include the serial lines on the management processor. Ports are numbered as follows:
•
1 — UPS/AUX Port
•
2 — Console Port
•
3 — Modem/Remote Session
•
4 — Local Session
Note: The “Console” may be selected for Console-In/Out, and would therefore be discovered as ttyS0.
UARTs are numbered consecutively starting with ttyS0. The following examples illustrate this:
•
rx2600 without a management processor (built-in UART select for Con-In/Out)
ttyS0: Serial [A|1]
ttyS1: Serial [B|2]
Note: This will have the same ordering if there are no UARTs selected for Console-In/Out.
•
rx2600 with a management processor (built-in UART select for Console-In/Out)
ttyS0: Serial [A|1]
ttyS1: Serial [B|2]
ttyS2: UPS/AUX Port
ttyS3: Console Port
ttyS4: Modem/Remote Session
ttyS5: Local Session
Note: This will have the same ordering if there are no UARTs selected for Console-In/Out.
•
rx2600 with a management processor (management processor console selected for Console-In/Out)
ttyS0: Console Port
ttyS1: Serial [A|1]
ttyS2: Serial [B|2]
ttyS3: UPS/AUX Port
ttyS4: Modem/Remote Session
ttyS5: Local Session
Why does Linux default to a VGA console after I’ve set up a serial console
for firmware, and how do I fix it?
Even if you set up a serial console for firmware, Linux defaults to a VGA console. If no VGA device is present,
console output goes to a dummy device (i.e. not to anything visible).
To specify a serial console, you must pass the console= parameter to the kernel. This can either be done as
an extra parameter to the kernel or by means of append=line in elilo.conf. For example:
--- manual boot option:
fs0:\> elilo linux "console=ttyS0"
ELILO boot: linux console=ttyS0
--- automatic via elilo.conf:
How does the Linux kernel order serial ports (UARTs)?
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