Boot hangs without monitor attached?

[nurbles]

I'm using TinyCore linux in an acrosser AR-ES0631.  We were surprised to discover that it refuses to boot when the monitor is not connected. In fact, we tried the following:

  BOOT?  Condition
  -----  --------------------------------------
   OK    Monitor connected, powered on
   OK    Monitor connected, powered off
   OK    Monitor connected, unplugged from AC
  fail   No monitor connected
  fail   KVM connected (monitor in any of above states)

The failure mode is that the system is hung (though Ctrl+Alt+Del still works if we attach a keyboard) and the display shows a blank, text mode screen with a hardware cursor blinking in the top left corner.

I've tried using the minimal Core version, booted from a USB stick made with from Core-current.iso with the latest Universal USB Installer (both downloaded today, Dec 6, 2013).  Strangely, the default is to boot into the same graphical screen that the TinyCore version boots into (by putting 'cde' on the kernel command line) even though the Core version is not supposed to include X.  I also tried all of the tests with 'cde' removed and with 'cde' replaced by 'text' and always saw a hang in the same way, under the same conditions.

I'm hoping someone can help me figure out how to get linux to stop trying to probe the monitor -- or whatever it is doing that is causing it to hang when the monitor is unplugged from the VGA port.

[gerald_clark]

Try the 'text' boot code so it does not try to launch X without a monitor.

[tinypoodle]

Third party installers are not supported (and known to frequently not produce desired result).

[curaga]

It's usually the BIOS that needs a monitor, if you don't get a "text" boot to work. There is nothing in TC that would prevent it.

edit:
According to a previous thread, it may be a bad interaction with your BIOS and your bootloader:
http://forum.tinycorelinux.net/index.php?topic=15708.0

[nurbles]

As stated in my original question, 'text' mode does not help, but other distros that I've booted from USB sticks made with the Universal USB Installer work fine with no monitor attached.  I'll try to get a CDROM attached today to conclusively prove (or not) that TC is the issue.

[gerald_clark]

Most of my TC machines have neither monitor nor keyboard attached, so it is not a TC issue.

[Rich]

Hi nurbles

... but other distros that I've booted from USB sticks made with the Universal USB Installer work fine with no monitor attached.

That may be, but Tinycore is not like other distros. You are not the first person who has reported having some sort of
problem after using the  "Universal" USB Installer. You might want to at least consider using an installer meant for
Tinycore to eliminate that as the source for this and possibly other problems down the road. If you need one that runs
under Windows, there is a download link located here:
http://tinycorelinux.net/faq.html#pendrives
It is called  Core2usb

[nurbles]

I managed to get a CDROM attached to one of our boxes, downloaded and burned a clean, unadulterated Core-current.iso to a CDROM (on my regular desktop computer) and booted from the CDROM.  TC boots almost instantly to the text $ prompt, as expected.

EXCEPT...

When there is no monitor connected to the VGA port, it hangs.  It does not get far enough in the boot process to start the network (the regular text mode boot starts it with DHCP, but my DHCP server doesn't see a request).  When I connect a monitor to the VGA port, I see a blank screen with the hardware cursor blinking at the top left.

This DOES NOT HAPPEN with other flavors of linux that I have tried.  It most assuredly *IS* a TinyCore issue!  I'm sure it is an issue that TC has with our hardware (based on a Geode processor), but since other versions of linux DO NOT manifest the issue, it MUST be in TC somewhere.

FWIW, we have worked around this (for now) but building simple VGA dongles that connect the monochrome monitor ID pin to ground.  That satisfies whatever is hanging and allows TC to boot normally.

Overall, I like TC best of all the small/tiny linux distros I've tried, partly because I have a well known procedure for building a compact flash version from an ISO, and partly because of all of the available 'extras' (in the form of the TCZ files) that few, if any others have.  I hope someone can figure out what is happening and correct it.

[gerald_clark]

How can you be sure it is not  the bios complaining about no monitor.
If the boot loader does not load Core, it is not a Core problem.

[Rich]

Hi nurbles

How can you be sure it is not  the bios complaining about no monitor.
If the boot loader does not load Core, it is not a Core problem.

FWIW, we have worked around this (for now) but building simple VGA dongles that connect the monochrome monitor ID pin to ground.

Maybe you can get some more insight into the problem by building a cable that just brings out the video signal, so maybe
the system doesn't know a monitor is connected. Then watch and see if you get messages from the BIOS, bootloader,
kernel, etc. and see where it hangs.

[tinypoodle]

You could try to log via netconsole:

http://forum.tinycorelinux.net/index.php/topic,13088.msg72103.html#msg72103

[nurbles]

gerald_clark:  I'm sure it isn't a bios issue because the machine will boot into the bios setup screens (not to mention DOS, ttylinux, damn small linux, and several others) without a monitor attached.  Only booting TC hangs.

rich:  we don't have a full time hardware person right now, so I'll need to wait until he's back in the office to try building a special cable.  However, it has always been my experience (in the past) that anything written to a text mode display is in memory and will be displayed as soon as a monitor is connected.  When I connect a monitor to a hung TC, the screen is blank, except for the hardware cursor.

tinypoodle:  in order to follow your suggestion, I must build my own TC boot image.  That would just open a whole new can of worms by allowing everyone here to blame my build procedure, settings, environment, whatever for the problem.  No, I'm working with clean TC ISO images, downloaded directly from links on tinycorelinux.net, burned to CD and booted in one of our embedded boxes with an IDE CDROM as the only attached disk drive.

EVERY other OS that I've put on CD and tried to boot without a monitor has worked.  TC hangs.  I was even able to boot a Ubuntu 12 installer CD I had up to the first GRAPHICAL screen in the installer -- it did not hang -- and when I connected a monitor, the graphical screen was presented!

[gerald_clark]

What ISO?
The ISOs are designed to be used to install core to a hard drive or flash drive.
They are useless on a headless machine with no persistent storage.
Install core to a hard drive or flash drive. Then try booting in text mode with no monitor.

[Rich]

Hi nurbles

When I connect a monitor to a hung TC, the screen is blank, except for the hardware cursor.

I know, you mentioned it in your original post, but a blank screen does not tell you why it's blank:
1. Did the BIOS not print any messages
2. Did the BIOS print messages, do a clear screen, and then hang
3. Did the BIOS do a screen clear and the bootloader hung when it tried to start
4. etc.

[tinypoodle]

tinypoodle:  in order to follow your suggestion, I must build my own TC boot image.  That would just open a whole new can of worms by allowing everyone here to blame my build procedure, settings, environment, whatever for the problem.  No, I'm working with clean TC ISO images, downloaded directly from links on tinycorelinux.net, burned to CD and booted in one of our embedded boxes with an IDE CDROM as the only attached disk drive.

Then look into setting up a serialconsole to get output.