[Bradford] Formatting micro SD for Raspberry Pi

[Moanin]

Hi John,

That's got me perplexed! Is the 32768 the bs=1M multiple? Each time an 
SD card is formatted it loses some space. These two are now down to 
29.??gb (the older one) and 31.?? (the new one). Which raises the 
question: do we need to stipulate the size, or, as I suspect, isn't it 
just as good to let whichever utility supply a default, which should be 
the end of the disc?

Alternatively, is 32768 the number of blocks in a section? That amounts 
to 4gb and is the size of the sections which were causing the problems 
earlier.

Or does 32768 simply state a maximum limit for the dd command?

The original dd command was:

dd if=/dev/zero of=/dev/sdb bs=1M status=progress
which gave me a constant update of, well, progress.

Now this has popped up in the browser (well I did do a search): 
https://www.iottechtrends.com/format-sd-card-for-raspberry-pi/
the implication of which appears to be that the dd command for 
installing the image will implement the partitioning, too.

That looks attractive, in part because of its simplicity. It also shows 
me that I neglected to unmount the card before formatting it during the 
earlier efforts.

But will it work? It implies using dd for the whole process.

TIA,

Mike

On 15/03/2021 22:02, John Robert Hudson wrote:
> Hi Mike
> 
> 
> With a 32GB card you should be using something like:
> 
> 
> dd if=/dev/zero of=/dev/sdb bs=1M count=32768
> 
> 
> The DOS partition is presumably for /boot/efi and the Ext4 partitions 
> for / and /home - no swap?
> 
> 
> I would use Gparted for that.
> 
> 
> John
> 
> 
> On Monday, 15 March 2021 21:08:44 GMT Moanin via Bradford wrote:
> 
>  > Evenin' All,
> 
>  >
> 
>  > I have two 32gb micro SD cards, the second because the first one
> 
>  > appeared to be corrupted. Once loaded with an OS, there were loads of
> 
>  > 4gb sectors at the beginning and the OS update in the Pi showed not
> 
>  > enough space left on the card. It needed a few more mb on the partition.
> 
>  > But it wasn't the card. This has repeated itself with each attempt to
> 
>  > fix matters.
> 
>  >
> 
>  > Wiping the cards then checking with either lsblk or fdisk -l showed them
> 
>  > as clean. So the formatting process came under suspicion and I was extra
> 
>  > careful when formatting them. So the OS transfer (using dd) became the
> 
>  > main suspect.
> 
>  >
> 
>  > They wee cleaned using the command "dd if=/dev/zero of=/dev/sdb bs=8192"
> 
>  > (earlier attempts were with bs=1M) and everything shows as 512 bytes
> 
>  > from fdisk -l /dev/sdb. The result has not changed with the altering of
> 
>  > the bs size parameter. It looks OK to me. Is it correct? As we would 
> expect?
> 
>  >
> 
>  > All of the above was using a CentOS 7 for Pi download but it may be
> 
>  > corrupted (the cause) and no Pi version is available any more. So
> 
>  > Raspberry Pi OS (Raspbian has been renamed, still Debian based) is about
> 
>  > to be downloaded.
> 
>  >
> 
>  > Here's the question: what is the best format structure for one of these
> 
>  > micro SDs prior to installing it? I really don't want to end up going
> 
>  > round in more frustrating and time consuming circles.
> 
>  >
> 
>  > The various online docs show a dos partition table with a 512M ext4
> 
>  > primary partition and another ext4 primary partition for the remainder
> 
>  > of the card. I've been using fdisk to do the formatting. Would Parted do
> 
>  > a better job, or stick with fdisk?
> 
>  >
> 
>  > If fdisk and dos table, is it safe to just hit o (create a new empty dos
> 
>  > partition table) to begin with?
> 
>  >
> 
>  > TIA,
> 
>  >
> 
>  > Mike
> 
>  >
> 
>  > --
> 
>  > Bradford mailing list
> 
>  > Bradford at mailman.lug.org.uk
> 
>  > https://mailman.lug.org.uk/mailman/listinfo/bradford
> 
> 
>