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Date:      Tue, 29 Nov 2011 16:42:34 -0800
From:      David Newman <>
Subject:   serial console access on ZFS server
Message-ID:  <>

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I'm having difficulty gaining serial console access to an 8.2-RELEASE
box running ZFS on its root partition. I would appreciate pointers to
help determine if this is a FreeBSD issue, or something external like
BIOS or cabling.

The server is a vanilla 1U Supermicro motherboard with AMI BIOS. The
BIOS is configured to run headless and to allow remote access via COM1.
There is no monitor, keyboard, or mouse attached.

FreeBSD is configured to use ZFS in all partitions. The server works
fine in all regards except wrt serial access.

/boot/loader.conf has this:


/boot.config has this:


and /etc/ttys has this:

ttyu0	"/usr/libexec/getty std.9600"	vt100	on  secure

The machine shows that tty exists:

# ls -l /dev/ttyu0
crw-------  1 root  wheel    0,  36 Nov 29 14:02 /dev/ttyu0

But there doesn't appear to be a device bound to it:

# grep -i 'irq 4' /var/run/dmesg.boot
uart0: <16550 or compatible> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
# ls -l /dev/uart0
ls: /dev/uart0: No such file or directory
# ls -l /dev/acpi0
ls: /dev/acpi0: No such file or directory

I'm attempting to connect via a known-good null modem cable (DB9 on both
ends) and a known-good USB serial dongle attached to my Mac, using the
Zterm program. This setup works fine for other serial devices.

Thanks in advance for troubleshooting clues.


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