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booting a pi without an SD card

Posted: Wed Jun 26, 2013 6:02 pm
by cairnarvon
What would you see on the screen if you did this? For example with no SD card or a blank SD card?

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 6:05 pm
by raspberrypiguy1
You would see absolutely nothing at all... Just a blank screen

The Raspberry Pi Guy

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 6:08 pm
by duberry
iv heard

with model A in some case you can boot from usb

with model b you need sdcard( fat boot partition ) to boot

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 6:25 pm
by CopterRichie
Sure would have been nice to have network booting. Maybe Rev. C.

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 7:45 pm
by jawbonegroove
sd boot + netboot + usb boot + nand boot partition + serial terminal +config.txt boot_priority=1

(1 == "yespleasek?")

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 9:14 pm
by alexeames
CopterRichie wrote:Sure would have been nice to have network booting. Maybe Rev. C.
If you take the SD card out, you'll have notwork booting. Will that do? :lol:

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 9:18 pm
by jawbonegroove
it'd be nice, for all the practicality of remote pi access, to be able to determine boot through software. see my last.

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 9:40 pm
by redhawk
Even if you could boot from USB there wouldn't be much point when you need the USB port for keyboard, mouse, wifi or even LAN functionality.

Richard S.

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 10:18 pm
by jawbonegroove
right now i'm running arch xfce headless over vnc ... from basically anywhere in the world. if i was abroad, i might like the option of booting from two or three sources. or keep a failsafe image on a usb stick for a server i only physically see once a month. or stick a recovery shell in a nand boot.

Re: booting a pi wihtout an SD card

Posted: Wed Jun 26, 2013 10:51 pm
by mahjongg
There is no BIOS ROM in the PI, just a very small bit of boot code for the GPU.

the boot code in the PI's GPU is very simple, and cannot handle a USB memory device behind a hub. Thats why its theoretically possible on a model A to boot from USB, but not on the model B which has a hub built in.
AFAIK, although is is claimed to be possible in theory, I have never read about anybody who actually demonstrated booting via USB! :|

Also, as the PI has only a single USB port, so you can either boot the PI through USB, OR use the USB port for something else, but not both! As the moment you try to add a hub to the equation, USB booting stops being possible!

So in any practical sense USB booting isn't a sensible option.

Bit this limitation isn't a big deal, as the PI can simply do only the first boot stage from the SD-card, but then switch over to something else for the rest of the boot process! Thats should be enough for all normal applications. You could use a (micro) SD-card soldered to the board, for that first stage, but still do the real booting from a thumb drive (or whatever else you fancy).

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 12:50 am
by Joe Schmoe
AFAIK, although is is claimed to be possible in theory, I have never read about anybody who actually demonstrated booting via USB!

Also, as the PI has only a single USB port, so you can either boot the PI through USB, OR use the USB port for something else, but not both! As the moment you try to add a hub to the equation, USB booting stops being possible!

So in any practical sense USB booting isn't a sensible option.
1) I'm 98% sure that at least one of dom or one of the other "top dogs" here has done it - and reported so on this board. There was a discussion of it a few months ago, and they said that it had been done (by them).

2) It occurs to me that the only way(s) you'd be able to tell that it worked (that it had, in fact, booted) would be:
a) You would see stuff on the HDMI (or composite) screen. Also audio. But, as noted, you wouldn't be able to mouse or keyboard anything.
b) You could log in and interact normally via the serial port.

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 1:48 am
by rpdom
Joe Schmoe wrote:
AFAIK, although is is claimed to be possible in theory, I have never read about anybody who actually demonstrated booting via USB!

Also, as the PI has only a single USB port, so you can either boot the PI through USB, OR use the USB port for something else, but not both! As the moment you try to add a hub to the equation, USB booting stops being possible!

So in any practical sense USB booting isn't a sensible option.
1) I'm 98% sure that at least one of dom or one of the other "top dogs" here has done it - and reported so on this board. There was a discussion of it a few months ago, and they said that it had been done (by them).
Yes, I remember seeing that one of the RPF have done a USB boot of sorts on a model A. I believe it worked in OTG mode, so had to be connected to a PC running special software. This doesn't really help us though.

TBH I don't really see the problem. You can use a low capacity SD card, even a cut down one so it doesn't protrude - glue it in place if you must, or solder it on wires so you can remove it if it fails, and set the kernel parameters to have a USB or NFS root file system.

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 3:10 am
by ChromeBlue
redhawk wrote:Even if you could boot from USB there wouldn't be much point when you need the USB port for keyboard, mouse, wifi or even LAN functionality.

Richard S.
A hub fixes that problem.

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 4:51 am
by rpdom
ChromeBlue wrote:
redhawk wrote:Even if you could boot from USB there wouldn't be much point when you need the USB port for keyboard, mouse, wifi or even LAN functionality.

Richard S.
A hub fixes that problem.
No. The USB boot on the Pi won't work through a hub. It uses USBOTG, where the Pi is the USB slave device and needs to be conected to a USB host/master device (like a PC).

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 12:54 pm
by solar3000
I use the default raspbian.
A newly created SD has two partitions, a vfat and a linux.
I haven't tried it yet, but I would guess if I modified the vfat files to go and mount a USB flash drive or a hard drive on a USB hub, it would use the USB flash drive instead of the SD card partition 2.
Then I would guess after boot up I would get:
SD card partition 1 ==> /boot
USB flash/hard drive ==> /

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 1:48 pm
by rpdom
solar3000 wrote:I use the default raspbian.
A newly created SD has two partitions, a vfat and a linux.
I haven't tried it yet, but I would guess if I modified the vfat files to go and mount a USB flash drive or a hard drive on a USB hub, it would use the USB flash drive instead of the SD card partition 2.
Then I would guess after boot up I would get:
SD card partition 1 ==> /boot
USB flash/hard drive ==> /
Yes, this is very common and fairly easy to do. I use a USB hard drive on one Pi.

Also, for a while I had it so that the / filesystem was on a networked share, but my server is slow and the performance wasn't good. It did mean I could access the Pi file system from other computers when it was switched off, which was good :)

Re: booting a pi wihtout an SD card

Posted: Thu Jun 27, 2013 6:31 pm
by solar3000
rpdom wrote:
solar3000 wrote:I use the default raspbian.
A newly created SD has two partitions, a vfat and a linux.
I haven't tried it yet, but I would guess if I modified the vfat files to go and mount a USB flash drive or a hard drive on a USB hub, it would use the USB flash drive instead of the SD card partition 2.
Then I would guess after boot up I would get:
SD card partition 1 ==> /boot
USB flash/hard drive ==> /
Yes, this is very common and fairly easy to do. I use a USB hard drive on one Pi.

Also, for a while I had it so that the / filesystem was on a networked share, but my server is slow and the performance wasn't good. It did mean I could access the Pi file system from other computers when it was switched off, which was good :)

Yeah I was thinking of a networked filesystem over wifi but I think that would give me a heart attack because of the random disconnects.

Re: booting a pi without an SD card

Posted: Fri Jun 28, 2013 2:24 am
by jawbonegroove
i suppose you could alternate loop images.