why won't my Rasp Pi boot without keyboard, video connected

[bobicanprogram]

I have enabled ssh and can connect to my Raspberry Pi from my Linux desktop.

However if I physically disconnect the keyboard, mouse and video but leave the network connect in, my Raspberry Pi won't boot. I have power as indicated by the red LED. I get a brief flicker on the green LED but then nothing. If I reconnect the keyboard, mouse and video it boots fine and I can ssh into the box.

Thanks in advance for your responses.

bob

[FTrevorGowen]

I have enabled ssh and can connect to my Raspberry Pi from my Linux desktop.

However if I physically disconnect the keyboard, mouse and video but leave the network connect in, my Raspberry Pi won't boot. I have power as indicated by the red LED. I get a brief flicker on the green LED but then nothing. If I reconnect the keyboard, mouse and video it boots fine and I can ssh into the box.
...

A Pi should boot and run O.K. in "headless" mode (no KVM as you describe) and my first Pi (a "B1", 256Mb) has been used that way since last summer - the only thing plugged into a USB port being a memory stick on which a MoinMoin wiki is run (used for my "Pi notes"). Have you tried just plugging in one of each device to see what's needed? Without an HDMI lead the Pi will still be generating "low res" video via the yellow RCA socket. Connecting that to the (yellow) A/V socket (or via a SCART adapter) on a TV may display some early boot info. that may "give us a clue". What model Pi are you using and what O.S? Have you been shutting down correctly (eg. "sudo shutdown -h now") from your ssh login before unplugging the Pi's PSU? If not you probably have corrupted your SDHC card image which has led to this strange behaviour.
Trev.

[bobicanprogram]

Thanks for your response. I have the model B with a prebuilt Debian SD card all from Newark Canada.

I have always used

sudo shutdown -h now

to shutdown from my ssh. Just did some more experiments to see which parts are needed. If I unplug the keyboard and mouse it boots fine. However if I unplug my HDMI to VGA dongle it won't boot. Any thoughts?

Thanks again in advance.

bob

[bobicanprogram]

Now this is wierd. It won't boot with the HDMI disconnected, but it will boot with the HDMI to VGA dongle plugged into the HDMI port but not connected to anything!!!

Any thoughts?

bob

[FTrevorGowen]

Now this is wierd. It won't boot with the HDMI disconnected, but it will boot with the HDMI to VGA dongle plugged into the HDMI port but not connected to anything!!!

Any thoughts?

bob

I haven't used any HDMI to VGA dongles myself but, IIRC according to the wiki and other forum posts one "has to take some care with them" - some (unpowered types) try to draw too much current from one of the HDMI pins, burning out a protection diode. Is yours a powered device? Do you also power your Pi (separately) via its micro USB connector. It's possible that the Pi is now getting (some of) its power from that dongle. If you post more info. about it, hopefully someone else may be able to enlighten us. It's probably worth checking the wiki's "verified peripherals list" at http://elinux.org/RPi_VerifiedPeripherals too.
Trev

[abishur]

First off, I also use an old Model B 256MB as a headless device with no problems so it can be done

I have the model B with a prebuilt Debian SD card all from Newark Canada.

Anytime I see the phrase "prebuilt SD card" I cringe a little The RPF team does a lot of work to fix various issues that come to light due to so many people using it in so many ways that they never thought it would be used for!

So my first thought is to do a quick format of your SD card and reimage it with the latest image, but that's just a knee jerk reaction

It won't boot with the HDMI disconnected, but it will boot with the HDMI to VGA dongle plugged into the HDMI port but not connected to anything!!!

This is where I really think the issue is, it sounds somewhat like you might have a ground issue that is being resolved by having the HDMI->VGA device plugged into the HDMI port. I'm not sure of the solution for that, but I have seen it mentioned around the forums

[bobicanprogram]

How could it be a power or ground issue, when the thing boots with the dongle connected to the Raspberry Pi but disconnected from the world? (it also boots fine with dongle connected to the VGA cable leading to my monitor). To eliminate the dongle, I tried plugging a straight HDMI cable into the connector (not connected to anything). It boots!!! So it has nothing to do with the dongle, but rather something to do with having something physically in the HDMI socket.

When the thing boots everything appears to work as advertised.

Strange one.

bob

[Jim JKla]

Sounds like there's some sort of fault in your HDMI plug shorting out that isolates when you plug into it.

I once had a cheap walkman clone the kind that had a speaker that failed when the headphones were plugged in the tabs that isolated the internal speaker caused a short when you plugged in the phones. In that case it was a small shard froma case drilling.

[abishur]

How could it be a power or ground issue, when the thing boots with the dongle connected to the Raspberry Pi but disconnected from the world?

Like I said, I don't know the why of it (I never had to worry about it so I didn't read too carefully), but I do remember the general scenario and people have explained the exact same situation with the exact same solution and it was something about ground or a short. Sorry I'm not being more helpful here, but hopefully I can at least get you pointed in the right direction

Edit: Ah Jim posted the same thing, from what you're describing that's really the direction to search the forums for for more information

[tosuzu]

I'm sorry for the necro but I search google and this is the only forum I can reply.

I solved this issue by editing the /boot/config.txt by enabling two options
Enable hdmi_safe=1 and hdmi_force_hotplug=1 by adding it to the end of file or removing the #.

I guessing that since hdmi_force_hotplug=1 is forcing the pi to use hdmi the pi is searching for a resolution to use and since nothing is plugged in, it hangs during boot so hdmi_safe forces it to use a default "catch-all" for the hdmi to use.

[Tellus-Jason]

@tosuzu Thanks for your response. It led me down the right path. Here is supporting info: viewtopic.php?p=437084#p437084 (search for "Here is a list of known causes why the Pi might not be booting, or might appear not to be booting:" and then "Video")

[alphanumeric]

"prebuilt Debian SD" << Debian as in Raspbian? Do you have a spare SD card? I would do up a second card with the latest Raspbin image on it and see how that works. Or redo your current card if you don't have a spare. I'm running Zero's, A+'s and 3B's here headless with no issues. It sounds like its something to do with the current OS on your SD card.