Raspberry Pi Boot Woes

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Raspberry Pi Boot Woes

Postby rmcwho901 » March 7th, 2015, 4:18 pm

Hello, I am a total noob at this kind of stuff, please help if you can.
SYSTEM: Raspberry Pi Model B+

Basically I have two problems.

1). I can boot things off NOOBS, however when i want to change the OS, my micro SD has significantly decreased in size. I doubt that I have exceeded the Read/Write limit of the card, what i think has happened is my previous operating system is still stored on the card, but i cannot access it to delete it. If you know what I am doing wrong please help.

2). I want to eventually install Kali Linux or PwnPi on my RPI (Both are built for pentesting). I am on a mac, and i cannot figure out how to 'image' the os on to the card. PwnPi comes in a file.img.7z, which i can unzip to get the .img file, but i don't know how to dd it on to the card. Kali Linux comes in a file.img.xz format, which I know nothing about. Is the .xz file similar to a compressed .zip or .7z? And after that, if i get a file.img, how to i dd it onto the card on a mac?

Thanks for all the help.
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Re: Raspberry Pi Boot Woes

Postby st2000 » March 9th, 2015, 6:17 am

rmcwho901 wrote:1). I can boot things off NOOBS, however when i want to change the OS, my micro SD has significantly decreased in size. I doubt that I have exceeded the Read/Write limit of the card, what i think has happened is my previous operating system is still stored on the card, but i cannot access it to delete it. If you know what I am doing wrong please help.


Are you looking at the SDCard on a Windows box? Windows assumes more and more that everyone is only using Windows. For instance, a Windows box assumes there is only 1 partition on an SDCard. If there are more partitions Windows will never see them. And, more recently, Windows completely stopped putting partition information on SDCards.

You will have to look up exactly what NOOBS does for the particulars. But I assume NOOBS will re-partition your SDCard into several "disks" using the appropriate formats (i.e. ext and / or fat) as a 1st step in preparing its self for use as the main mass storage for a Linux / RaspberryPi box. And do this automatically. That is, you do need a minimum SDCard size card. But I believe the re-partitioning script will automatically detect and extend the partitions so as not to wast any SDCard capacity.

To re-create the SDCard on a Linux computer like Ubuntu or Fedora it is a simple 1 line command using the Disk Dump utility ("dd <input> <output>"). To get around Windows short comings you need a utility that can write an disk image to the SDCard.

rmcwho901 wrote:2). I want to eventually install Kali Linux or PwnPi on my RPI (Both are built for pentesting). I am on a mac, and i cannot figure out how to 'image' the os on to the card. PwnPi comes in a file.img.7z, which i can unzip to get the .img file, but i don't know how to dd it on to the card. Kali Linux comes in a file.img.xz format, which I know nothing about. Is the .xz file similar to a compressed .zip or .7z? And after that, if i get a file.img, how to i dd it onto the card on a mac?


A MAC? Hum, all I know is that a MAC is a Unix computer (since OSX I believe). Note, the Disk Dump utility is very simple and very dangerous. You usually have to run it as the root user and as such have the power to wipe out your main HDD if you mistakenly specify your main HDD as the target. Most Unix computer have help built in. Try "man dd" and see if the "man"ual page for Disk Dump is available. Do be careful.

Alternatively, you might try to find a utility that takes the guess work (and possible danger) out of using the "dd" command directly. You are looking to write an image to an SDCard.

(FYI, A disk image is basically the raw data you want to write to a disk. Everything. That is why you are not being asked what format to use. It's already part of the disk image. This is also why a (for instance) FAT 2GB disk image written to a 16GB SDCard will then show up as a 2GB card. Because it now looks like a 2GB card.)
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Re: Raspberry Pi Boot Woes

Postby bandersnatch » March 9th, 2015, 12:51 pm

Yeah, to repeat st2000's wise words regarding "dd":

"...Do be careful..."
"...Do be careful..."
"...Do be careful..."

!!!! ;^)

This forum entry deals exactly with your problem:
raspberrypi.stackexchange.com/questions/4144/writing-img-file-to-sd-card-from-a-mac

It provides all the info you need if you REALLY wanna use "dd", and also has links to less dangerous GUI
tools for the same job...
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