Diff for /wikisrc/ports/evbarm/raspberry_pi.mdwn between versions 1.78 and 1.79

version 1.78, 2018/10/30 23:09:40 version 1.79, 2018/10/30 23:13:40
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 ## Booting  ## Booting
   
 The device boots by finding a file "bootcode.bin".   The primary location is a FAT32 partition on the uSD card, and an additional location is on a USB drive.  See the [[upstream documentation on booting]](https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/) and read all the subpages.  The device boots by finding a file "bootcode.bin".   The primary location is a FAT32 partition on the uSD card, and an additional location is on a USB drive.  See the [upstream documentation on booting](https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/) and read all the subpages.
   
 The standard approach is to use a uSD card, with a fdisk partition table containing a FAT32 partition marked active, and a NetBSD partition.  The NetBSD partition will then contain a disklabel, pointing to an FFS partition (a), a swap paritiion (b) and the FAT32 boot partition mounted as /boot (e).  The file /boot/cmdline.txt has a line to set the root partition.  The standard approach is to use a uSD card, with a fdisk partition table containing a FAT32 partition marked active, and a NetBSD partition.  The NetBSD partition will then contain a disklabel, pointing to an FFS partition (a), a swap paritiion (b) and the FAT32 boot partition mounted as /boot (e).  The file /boot/cmdline.txt has a line to set the root partition.
   
Line 169  One wrinkle in the standard approach is  Line 169  One wrinkle in the standard approach is 
 An alternate approach is to have the boot FAT32 partition as above, but to have the entire system including root on an external disk.  This is configured by changing root=ld0a to root=sd0a or root=dk0 (depending on disklabel/GPT).  Besides greater space, part of the point is to avoid writing to the uSD card.  An alternate approach is to have the boot FAT32 partition as above, but to have the entire system including root on an external disk.  This is configured by changing root=ld0a to root=sd0a or root=dk0 (depending on disklabel/GPT).  Besides greater space, part of the point is to avoid writing to the uSD card.
   
 A third approach, workable on the Pi 3 only, is to configure USB host booting (already enableed on the 3+; see the upstream documentation) and have the boot partition also on the external device.  In this case the external device must have an MBR because the hardware's first-stage boot does not have GPT support.   \todo Explain if this has been observed to work.  A third approach, workable on the Pi 3 only, is to configure USB host booting (already enableed on the 3+; see the upstream documentation) and have the boot partition also on the external device.  In this case the external device must have an MBR because the hardware's first-stage boot does not have GPT support.   \todo Explain if this has been observed to work.
 \todo In theory the [[procedure to program USB host boot mode]](https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md) will function on a NetBSD system because the programming is done by bootcode.bin.  \todo In theory the [procedure to program USB host boot mode](https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/msd.md) will function on a NetBSD system because the programming is done by bootcode.bin.
   
 \todo Explain USB enumeration and how to ensure that the correct boot and root devices are found if one has e.g. a small SSD for the system and a big disk.  \todo Explain USB enumeration and how to ensure that the correct boot and root devices are found if one has e.g. a small SSD for the system and a big disk.
   

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  Added in v.1.79


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