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On Thu, Jun 25, 2020 at 2:55 AM Robin Atwood <robin@×××××.org> wrote: |
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> |
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> On Wed, 24 Jun 2020 13:31:30 -0400 |
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> tedheadster <tedheadster@×××××.com> wrote: |
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> |
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> > Robin, |
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> > are you comfortable just going with a bare-bones console and build a |
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> > new kernel where you _disable_ CONFIG_FB? That might do it. |
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> > |
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> > Alternately, you can hook up a serial cable to another computer and |
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> > set "console=ttyS0,115200n8". |
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> |
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> I will try that, if it works it will at least give me a chance to look |
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> at the error messages. |
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> |
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> I don't think I have any serial cables! |
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> |
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While serial consoles are one solution, I'd take a look at network |
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consoles. They're FAR easier to manage on commodity hardware. All |
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you really need is another host on the network that can run netcat. |
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I stick this in my /etc/grub/default - or otherwise get it onto the |
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command line in the bootloader: |
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netconsole=@/,6666@192.168.1.1 |
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That tells the kernel to send all console output over UDP to |
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192.168.1.1:6666. If you have multiple interfaces/etc you might need |
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to expand that command line a bit. I have no idea how it comes up |
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with the sending IP - if you care about that you can specify it. I'm |
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guessing it doesn't run DHCP - but this is just plain UDP so it is |
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one-way and there is no need for acks to get back to the sender. |
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On the destination host I run: |
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nc -u -l -p 6666 |
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(nc is provided by the netcat package - a very basic tool that should |
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be available everywhere - probably on non-linux operating systems |
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also) |
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Start up the reception part before you try booting the host you're |
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troubleshooting, because it is just going to send packets blind into |
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the ether and if nothing is listening they're gone. Obviously |
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netconsole is a very simple implementation so that it can run during |
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early boot. It is very good for capturing panics/etc. |
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I don't know how it compares with serial console in terms of how early |
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it starts. I think it does capture stuff very early in boot though - |
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both systems require a degree of hardware initialization before they |
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can work, but both are also very simple. |
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This does need to be enabled in the kernel. |
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You can also enable this on a running kernel but of course that does |
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no good for issues during boot. Full docs are at: |
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https://www.kernel.org/doc/Documentation/networking/netconsole.txt |
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-- |
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Rich |
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