Strange parted behaviour

[Robert Moskowitz]

On 08/08/2014 02:32 PM, Chris Murphy wrote:
> On Aug 8, 2014, at 7:21 AM, Robert Moskowitz <rgm at htt-consult.com> wrote:
>
>> So I am making progress but saw a strange bit.
>>
>> #parted /dev/sdb mkpart uboot ext3 4 516
>>
>> # parted /dev/sdb print
>> Model: Generic- Multi-Card (scsi)
>> Disk /dev/sdb: 7969MB
>> Sector size (logical/physical): 512B/512B
>> Partition Table: gpt
>> Disk Flags:
>>
>> Number  Start   End     Size    File system  Name    Flags
>> 1      4194kB  516MB   512MB   fat32        uboot
>>
>> I formated it with:
>>
>> #mkfs -t ext3 /dev/sdb1
>>
>> # parted /dev/sdb print
>> Model: Generic- Multi-Card (scsi)
>> Disk /dev/sdb: 7969MB
>> Sector size (logical/physical): 512B/512B
>> Partition Table: gpt
>> Disk Flags:
>>
>> Number  Start   End     Size    File system     Name    Flags
>> 1      4194kB  516MB   512MB   ext3            uboot
>>
>> So why did parted mislabel the partition?
> Yeah you're getting confused. It's really easy. It didn't format it ext3, it just sets it to a partition type GUID for that filesystem, which in the version of parted you're using is for Microsoft basic data (i.e. it would not have made any difference had you chosen fat32 or ext3, because on GPT disks parted uses the same partition type code until you get to the Fedora 21 version and then choosing ext3 would make it a partition type GUID for "Linux filesystem".
>
> Parted is showing it as fat32 because it found a fat32 superblock. When you reformatted it ext3, parted found the ext3 superblock. So again, it's a throwback from when parted did formatting and fs resizing.
>
> The behaviors change silently (including flags) between MBR and GPT partition schemes too. So you have to be aware of what partition method is being used.

And after I did all the setup for GPT, it (the Cubieboard) would not 
boot.  So I looked at cards that I had that did boot, and THEY were all 
type msdos.  So back to the beginning making the card msdos, and can't 
label the partitions, oh, but finally rebuilt and I did create a 
bootable card!

So now I have a good cookbook that I will eventually be able to post to 
the Redsleeve wiki (what I am build).  Once I get the video to login, I 
will say success.  I only get login so far to the serial console.

>
> For example "boot" flag for MBR disks sets the active bit for a partition; whereas on GPT the "boot" flag changes the partition type GUID to that of "EFI System partition". Yeah I know, you're welcome to start shooting gin at any time but I guarantee you it doesn't really help. It's sorta like taking Percocet for pain and realizing it still hurts, you just don't care.
>
>
> Chris Murphy
>