View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000302 | file | General | public | 2021-12-04 03:35 | 2021-12-06 22:13 |
| Reporter | calestyo | Assigned To | christos | ||
| Priority | normal | Severity | minor | Reproducibility | have not tried |
| Status | assigned | Resolution | open | ||
| Product Version | 5.41 | ||||
| Summary | 0000302: GPT not correctly detected as such, because of it's protective MBR | ||||
| Description | Hey. A file that contains a GPT (GUID Partition Table) is nonetheless detected as MBR, which is probably because every GPT contains a protective MBR just at the position where the regular MBR would be. E.g.: # gdisk -l example.img GPT fdisk (gdisk) version 1.0.6 Partition table scan: MBR: protective BSD: not present APM: not present GPT: present Found valid GPT with protective MBR; using GPT. Disk example.img: 16777216 sectors, 8.0 GiB Sector size (logical): 512 bytes Disk identifier (GUID): C93252EC-C2A3-41C8-9A12-ECF030C66D7E 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 16777182 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 EF00 EFI system partition 2 67584 16777182 8.0 GiB 8300 Linux filesystem whereas file only detects the MBR: # file example.img example.img: DOS/MBR boot sector; partition 1 : ID=0xee, start-CHS (0x0,0,2), end-CHS (0x3ff,255,63), startsector 1, 16777215 sectors, extended partition table (last) Not really sure how one should (safely) detect a GPT. The protective MBR always looks like this: Expert command (? for help): o Disk size is 16777216 sectors (8.0 GiB) MBR disk identifier: 0x00000000 MBR partitions: Number Boot Start Sector End Sector Status Code 1 1 16777215 primary 0xEE i.e. always type 0xEE ... but that alone is AFAIU not enough to say there's a GPT... furthermore, GPTs may not use a protective MBR at all. The best is perhaps to just rely on the GPT signature, which is: EFI PART at 0x0 (and I think with respect to the endianess) (see https://en.wikipedia.org/wiki/GUID_Partition_Table#Partition_table_header_(LBA_1) ) Not sure if it makes sense to check for the backup GPT, probably not. Cheers, Chris. | ||||
| Tags | No tags attached. | ||||
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file just does not look after the MBR for the GPT information... It could be made to look, but currently it does not. |
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Guess that would make sense... just like it looks deeper into various container formats to find out what's actually inside. |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2021-12-04 03:35 | calestyo | New Issue | |
| 2021-12-06 20:06 | christos | Assigned To | => christos |
| 2021-12-06 20:06 | christos | Status | new => assigned |
| 2021-12-06 20:07 | christos | Status | assigned => feedback |
| 2021-12-06 20:07 | christos | Note Added: 0003682 | |
| 2021-12-06 22:13 | calestyo | Note Added: 0003683 | |
| 2021-12-06 22:13 | calestyo | Status | feedback => assigned |
