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I am not very experienced using Linux and I have the following situation that cause me some doubts.

I have wrote RaspBian (the RaspBerry linux distribution) on an SD card using this command on Ubuntu:

sudo dd if=2014-01-07-wheezy-raspbian.img of=/dev/sdb bs=1024

So if now I run the fdisk -l command I obtain that I have 2 partitions on my SD card:

Dispositivo Boot      Start         End      Blocks   Id  System
/dev/sdb1            8192      122879       57344    c  W95 FAT32 (LBA)
/dev/sdb2          122880     5785599     2831360   83  Linux

And now the first doubt: the dd command creates two partitions on the SD card:

  1. /dev/sdb1 that is a litle FAT32 partition (what it means (LBA)?)
  2. /dev/sdb2 that is a larger Linux ext3 partition

The question is: why it also creates a FAT32 partition and not only a Linux ext3 partition?

If I go into my computer resource I can see a device (related to my SD card) into the devices list that contains some RaspBian file, following a screenshot:

enter image description here

And if I see the property of this device I obtain this:

device properties

So, looking at the previous screenshot it seems to me that this is the small FAT32 partition, and now I have the followings doubts:

If it is the smallest FAT32 partition, what contains? The RaspBian boot or what?

Why, in the devices list, I have only the FAT32 partition and not also the Linux one (/dev/sdb2), to see it have I to mount it? How?

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1 Answer 1

up vote 2 down vote accepted

The partition table of a disk lives on sector 0. You can overwrite a disk's (SD card's, etc.) partition table by overwritng this sector with dd, which is what happened.

FAT32 is understood by both Linux and Windows systems. If you place an ext formatted disk or SD card in a Windows system, Windows will ask you to format it. If, however, you have a "buffer" FAT32 partition, Windows will mount and open that instead. Windows does not open or touch any other partition on a removeable drive or card other than the first. So this may have been done to prevent an accidental format in case it's put in a Windows system. (It also may be that the boot firmware of the RPi only understands FAT32 as well).

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