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Tracing boot progress on screen and serial console
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childofpeace
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Joined: 24 Nov 2013
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PostPosted: Sun Nov 24, 2013 3:24 pm    Post subject: Tracing boot progress on screen and serial console Reply with quote

Hello,

I have enabled serial console in my GRUB configuration and i got a problem. I can see GRUB on monitor and serial console. Also kernel logs are visible in both places. But messages coming from initramfs and init are not visible on my monitor. How can i fix this? I would like to see everything on both, serial console and my monitor. Is it possible?

I also find a problem with accessing GRUB via serial console. Looks like my cursors and function keys are not working. Any ideas?

Thanks!
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greyspoke
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Joined: 08 Jan 2010
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PostPosted: Mon Nov 25, 2013 12:03 pm    Post subject: Reply with quote

You will need to configure your initramfs to speak to the serial port. Are you making your own or using dracut or genkernel etc.?. You can use the console= boot parameter to direct where the kernel sends its console messages, but I think it will only send detailed messages to one place (the last console= setting). So if you passed the kernel console=/dev/tty1 console-dev/ttyS0 most messages would only appear on ttyS0.

I am still trying to get this to work with my home-made initramfs, but the problem is the serial port settings I think, I'll get back to you if I get it all working.
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childofpeace
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PostPosted: Mon Nov 25, 2013 4:56 pm    Post subject: Reply with quote

Yes i have added the folloeing to kernel parameters:

Code:
console=tty0 console=ttyS0,115200


and only kernel messages are put to both places. Everything else goes only to ttyS0.
Is it possible to let init push messages to both places?

I would also like to know how to use GRUB via serial port? When i press cursor up/down to choose proper selection, the menu reloads. This also prevents me from committing any changes to kerne parameters before bootup.
Actually i opened serial connection using the following command:

Code:
screen /dev/ttyS0 115200


P.S. I use better-initramfs
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greyspoke
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PostPosted: Mon Nov 25, 2013 5:24 pm    Post subject: Reply with quote

This is a good guide to serial console linux, it doesn't deal with initramfs it does deal with grub (grub-legacy that is). No doubt grub2 does, but I have no idea about that.

http://www.tldp.org/HOWTO/Remote-Serial-Console-HOWTO/

Can't help you with better-initramfs I am afraid. If it did allow for output to a serial port, it would probably be via a kernel command line option.
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childofpeace
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PostPosted: Mon Nov 25, 2013 7:09 pm    Post subject: Reply with quote

So looks like it is normal and i cannot get output to both destinations :(
Anyway i still dont know whats wrong with cursors. I would like to navigate through GRUB menu using them.
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greyspoke
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PostPosted: Tue Nov 26, 2013 10:24 am    Post subject: Reply with quote

I think how the arrow keys function are a bit dependent on what type of terminal your other computer is emulating and how your terminal client is set up. Trial and error may help, that's my approach. If you use a graphical terminal client like PuTTY, the various options are there for you to click and try.
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