Cannot install using serial console

Jeremy Chadwick freebsd at
Fri Sep 10 15:38:33 UTC 2010

On Fri, Sep 10, 2010 at 05:18:00PM +0200, Jeremie Le Hen wrote:
> On Fri, Sep 10, 2010 at 04:27:26AM -0700, Jeremy Chadwick wrote:
> > > > As far as I know you need also to enable a serial terminal in /etc/ttys.
> > > 
> > > Yeah, this came to my mind too but I check on the installation CD, there
> > > is no /etc/ttys.
> > 
> > This is normal.
> > 
> > Can you try hacking up a solution for yourself based on what I've
> > documented with regards to PXE booting?  There will be pieces which
> > obviously don't apply to you because you're booting from physical media,
> > but some of the adjustments (to the bootloader, etc.) you can try.
> > 
> >
> But as far as I understand the handbook, this is not required to perform
> the installation through sysinstall(8) on a serial console.  Modifying
> /boot/loader.conf on the installation media is enough according to
> chapter 2.12.1.  Am I wrong?

Nah you're not wrong -- I'm just not sure what the VM might be doing
with/to the serial port.  I don't know what KVM you're using on Linux,
but does the VM machine have a BIOS?  If so, does it offer something
like serial console redirect capability?  If so, and it's enabled, it
could/might be conflicting with the OS.

The reason I mention this: on some x86 systems that offer BIOS-level
console redirection capability, the kernel (confirmed on both FreeBSD
and Linux) can, depending on circumstances I'm not sure of, lock up the
OS hard.

If the VM offers such a feature and you're not using it, try it (and
remove the comconsole stuff from your loader.conf).  You might end up
with VGA-over-serial that way, and it might suffice.

I imagine some form of getty(8) must be in use under the FreeBSD
installation environment, because you can switch virtual consoles via
Alt-<F1/F2...> as I'm sure you know.

> > One thing worth pointing out is that you stated the system that you're
> > trying to use serial console on is actually running under a VM on Linux:
> > 
> > > I tried to install FreeBSD (201008 -CURRENT snapshot, but I don't think
> > > it's important here) in a KVM-backed virtual machine on a headless Linux
> > > host, following section 2.12.1 of the handbook.
> > 
> > Can you provide a full dmesg prior to the "/stand/sysinstal" output
> > happening?  You don't need to boot verbose (yet), but it would help with
> > regards to determining what the kernel is seeing device-wise.  Yes it
> > matters.
> Yes, I've actually already posted it in my original message:

Thanks much -- for some reason that part of the Email is missing for me.

uart0: <Non-standard ns8250 class UART with FIFOs> port 0x3f8-0x3ff irq 4 flags 0x10 on acpi0
uart0: [FILTER]
uart0: console (9600,n,8,1)

It sure looks like it's console, but I'm not sure if there are
implications/bugs that might stop serial I/O from working past a certain
point for this type of chip, especially when under a VM.

Only other things I can think of trying, one at a time:

- Explicitly set a serial port speed using comconsole_speed in
- Adding boot_serial="yes" to loader.conf
- Try booting with ACPI disabled.  I'm not sure this will work under a
  VM, but worth a shot I guess

| Jeremy Chadwick                                   jdc at |
| Parodius Networking              |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |

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