On Mon, Dec 09, 2019 at 10:45:46PM +0100, Antony Stone wrote:
> On Monday 09 December 2019 at 22:38:26, Hendrik Boom wrote:
>
> > I have an sd card that used to be in an android phone.
> > My usual tools tell me very little:
> >
> > root@midwinter:~# lsblk --fs /dev/sdb
> > NAME FSTYPE LABEL UUID MOUNTPOINT
> > sdb
> > ├─sdb1
> > └─sdb2
> >
> > root@midwinter:~# fdisk -l /dev/sdb
> > Disk /dev/sdb: 14.9 GiB, 15931539456 bytes, 31116288 sectors
> > Units: sectors of 1 * 512 = 512 bytes
> > Sector size (logical/physical): 512 bytes / 512 bytes
> > I/O size (minimum/optimal): 512 bytes / 512 bytes
> > Disklabel type: gpt
> > Disk identifier: 4F1502F0-81F3-49FA-A294-8B8FB4DB6964
>
> I'm really rather surprised that a 16Gbyte SD card is has a GPT partition
> table.

My guess is that Android put it there and that it's not what was on it
originally.

>

> > Device     Start      End  Sectors  Size Type
> > /dev/sdb1   2048    34815    32768   16M unknown
> > /dev/sdb2  34816 31116254 31081439 14.8G unknown
> > root@midwinter:~#

> >
> > Is there another way to find out anything?
>
> Well, given that it's got a GPT partition table, try sgdisk instead of sfdisk.
>
> > Or is this likely to be an Google-encrypted card I can do nothing with
> > except restore it to an almost virginal state?
>
> What do you *want* to do with it?
>
> Read it, copy it, reformat it, what?

Read it if I can (and I aready suspect I can't); otherwise reformat
it to whatever file system it is that most
consumer devices using microsd cards expect.
Kind of a factory reset.

>
> > And what is the proper way to reformat an sdcard to the file
> > systems just about everything accepts without using
> > up its remaining lifetime?
>
> Hm, dd if=/dev/zero of=/dev/sdb bs=1M count=1

Yes, that will clear it out. But what file system is customarily on a new
16G microsd card? And does that fs really need everything cleared out?

-- hendrik