SD card keeps restoring partitions

marianaf · 11-03-2020, 12:33 PM

Hello,

My SD card refuses to update the changes I 'write' with fdisk or gdisk. After making modifications (such as deleting or creating partitions) & rebooting or calling 'partprobe', the SD card old contents are back.
Anyone has an idea how to wipe everything out so to use it again? Thanks.

Code:

sudo gdisk /dev/sdb
GPT fdisk (gdisk) version 1.0.5

Partition table scan:
  MBR: hybrid
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with hybrid MBR; using GPT.

Command (? for help): p
Disk /dev/sdb: 31422464 sectors, 15.0 GiB
Model: Storage Device  
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): BF40D979-29F5-429B-B57F-29690F8CB39A
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 31422430
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048           67583   32.0 MiB    0C01  hassos-boot
   2           67584          116735   24.0 MiB    8300  hassos-kernel0
   3          116736          641023   256.0 MiB   8300  hassos-system0
   4          641024          690175   24.0 MiB    8300  hassos-kernel1
   5          690176         1214463   256.0 MiB   8300  hassos-system1
   6         1214464         1230847   8.0 MiB     8300  hassos-bootstate
   7         1230848         1427455   96.0 MiB    8300  hassos-overlay
   8         1427456        31422430   14.3 GiB    8300  hassos-data

Code:

sudo fdisk /dev/sdb

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

A hybrid GPT was detected. You have to sync the hybrid MBR manually (expert command 'M').

(to remove the 'A hybrid GPT was detected. You have to ...' message on gdisk I do:

Code:

Command (? for help): x

Expert command (? for help): n

Expert command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!

Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/sdb.
Warning: The kernel is still using the old partition table.
The new table will be used at the next reboot or after you
run partprobe(8) or kpartx(8)
The operation has completed successfully.

which seems to work, but then when attempting to delete the partitions with fdisk I get the error message:

Code:

sudo fdisk /dev/sdb

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p
Disk /dev/sdb: 14.101 GiB, 16088301568 bytes, 31422464 sectors
Disk model: Storage Device  
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: BF40D979-29F5-429B-B57F-29690F8CB39A

Device       Start      End  Sectors  Size Type
/dev/sdb1     2048    67583    65536   32M Microsoft reserved
/dev/sdb2    67584   116735    49152   24M Linux filesystem
/dev/sdb3   116736   641023   524288  256M Linux filesystem
/dev/sdb4   641024   690175    49152   24M Linux filesystem
/dev/sdb5   690176  1214463   524288  256M Linux filesystem
/dev/sdb6  1214464  1230847    16384    8M Linux filesystem
/dev/sdb7  1230848  1427455   196608   96M Linux filesystem
/dev/sdb8  1427456 31422430 29994975 14.3G Linux filesystem

Command (m for help): d
Partition number (1-8, default 8): 

Partition 8 has been deleted.

Command (m for help): d
Partition number (1-7, default 7): 

Partition 7 has been deleted.

Command (m for help): d
Partition number (1-6, default 6): 

Partition 6 has been deleted.

Command (m for help): d
Partition number (1-5, default 5): 

Partition 5 has been deleted.

Command (m for help): d
Partition number (1-4, default 4): 

Partition 4 has been deleted.

Command (m for help): d
Partition number (1-3, default 3): 

Partition 3 has been deleted.

Command (m for help): d
Partition number (1,2, default 2): 

Partition 2 has been deleted.

Command (m for help): d
Selected partition 1
Partition 1 has been deleted.

Command (m for help): p
Disk /dev/sdb: 14.101 GiB, 16088301568 bytes, 31422464 sectors
Disk model: Storage Device  
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: BF40D979-29F5-429B-B57F-29690F8CB39A

Command (m for help): w
The partition table has been altered.
Failed to remove partition 2 from system: Device or resource busy
Failed to remove partition 3 from system: Device or resource busy
Failed to remove partition 7 from system: Device or resource busy
Failed to remove partition 8 from system: Device or resource busy

The kernel still uses the old partitions. The new table will be used at the next reboot. 
Syncing disks.

and, after calling 'partprobe', I'm back with having 8 partitions & MBR:hybrid in gdisk)

Any hint would be highly appreciated.

smallpond · 11-03-2020, 12:48 PM

Writing to the disk has no effect on the kernel's partition table. To update that, do:

Code:

blockdev --rereadpt /dev/sdb

If any partition has a mounted filesystem, it must be unmounted first. If any partition has a volume group, it must be deactivated.

computersavvy · 11-03-2020, 12:52 PM

Code:

The partition table has been altered.
Failed to remove partition 2 from system: Device or resource busy
Failed to remove partition 3 from system: Device or resource busy
Failed to remove partition 7 from system: Device or resource busy
Failed to remove partition 8 from system: Device or resource busy

The kernel still uses the old partitions. The new table will be used at the next reboot. 
Syncing disks.

This might be a clue!
Was anything on the device mounted or in use when you ran gdisk? It says 4 partitions were busy.
Did you delete all the partitions or just modify something. I am not thoroughly familiar with the expert mode so your shorthand commands are greek to me. Looking at the commands for expert mode it seems you wrote a new protective mbr, but did not change any partitions. If you wanted a new partition table then an "o" from the standard menu gives that.
Did you reboot as suggested?

fatmac · 11-03-2020, 01:03 PM

Remove & re insert the card, the changes should then show - otherwise use dd to clear the first 4MB or so of the card, & then create a new partition table.

Hermani · 11-05-2020, 04:40 PM

Today I just learned that when SD cards get corrupted or damaged, they can go into some kind of read-only mode. If a SD card is giving you problems, please discard it and get a new one.

computersavvy · 11-05-2020, 11:01 PM

Quote:

Originally Posted by Hermani

Today I just learned that when SD cards get corrupted or damaged, they can go into some kind of read-only mode. If a SD card is giving you problems, please discard it and get a new one.

Yes, in that respect SD cards are similar to flash drives. When they get old and begin to reach EOL they go to read only (apparently to protect your remaining data)

beachboy2 · 11-06-2020, 03:06 AM

marianaf,

Welcome to LQ forums.

As others have stated, your SD card may be faulty and is now in read-only mode.

You could install dcfldd and then check the card (see post #9):
https://www.linuxquestions.org/quest...ly-4175682962/

Alternatively, you could just replace the SD card.

JJJCR · 11-06-2020, 06:13 AM

Some SD Card has a mechanical switch, to set the mode either to read only or read/write.

Have you checked this?