I experience relatively often that the partition table of a USB stick or SD card is suddenly no longer recognized by the kernel while (g)parted and fdisk still see it, as do other systems. I can even instruct gparted to do a fsck on one of the partitions but it fails of course because the device files let's say /dev/sdbX don't exist.
I'll attach the dmesg output:
[ 8771.136129] usb 1-5: new high-speed USB device number 4 using ehci_hcd [ 8771.330322] Initializing USB Mass Storage driver... [ 8771.330766] scsi4 : usb-storage 1-5:1.0 [ 8771.331108] usbcore: registered new interface driver usb-storage [ 8771.331118] USB Mass Storage support registered. [ 8772.329734] scsi 4:0:0:0: Direct-Access Generic STORAGE DEVICE 0207 PQ: 0 ANSI: 0 [ 8772.334359] sd 4:0:0:0: Attached scsi generic sg1 type 0 [ 8772.619619] sd 4:0:0:0: [sdb] 31586304 512-byte logical blocks: (16.1 GB/15.0 GiB) [ 8772.620955] sd 4:0:0:0: [sdb] Write Protect is off [ 8772.620971] sd 4:0:0:0: [sdb] Mode Sense: 0b 00 00 08 [ 8772.622303] sd 4:0:0:0: [sdb] No Caching mode page present [ 8772.622317] sd 4:0:0:0: [sdb] Assuming drive cache: write through [ 8772.629970] sd 4:0:0:0: [sdb] No Caching mode page present [ 8772.629992] sd 4:0:0:0: [sdb] Assuming drive cache: write through [ 8775.030231] sd 4:0:0:0: [sdb] Unhandled sense code [ 8775.030240] sd 4:0:0:0: [sdb] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE [ 8775.030249] sd 4:0:0:0: [sdb] Sense Key : Medium Error [current] [ 8775.030259] sd 4:0:0:0: [sdb] Add. Sense: Data phase CRC error detected [ 8775.030271] sd 4:0:0:0: [sdb] CDB: Read(10): 28 00 00 00 00 00 00 00 08 00 [ 8775.030291] end_request: I/O error, dev sdb, sector 0 [ 8775.030300] quiet_error: 30 callbacks suppressed [ 8775.030306] Buffer I/O error on device sdb, logical block 0 [ 8775.033781] ldm_validate_partition_table(): Disk read failed. [ 8775.033813] Dev sdb: unable to read RDB block 0 [ 8775.037147] sdb: unable to read partition table [ 8775.047170] sd 4:0:0:0: [sdb] No Caching mode page present [ 8775.047185] sd 4:0:0:0: [sdb] Assuming drive cache: write through [ 8775.047196] sd 4:0:0:0: [sdb] Attached SCSI removable disk
Here, on the other hand, is what parted has to say about the same disk, at the same time:
(parted) print Model: Generic STORAGE DEVICE (scsi) Disk /dev/sdb: 16.2GB Sector size (logical/physical): 512B/512B Partition Table: msdos Number Start End Size Type File system Flags 1 4194kB 62.9MB 58.7MB primary fat16 lba 2 62.9MB 16.2GB 16.1GB primary ext4
It's not only parted, even the older fdisk has no trouble with that partition table:
Command (m for help): p Disk /dev/sdb: 16.2 GB, 16172187648 bytes 64 heads, 32 sectors/track, 15423 cylinders, total 31586304 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 Disk identifier: 0x000dbfc6 Device Boot Start End Blocks Id System /dev/sdb1 8192 122879 57344 c W95 FAT32 (LBA) /dev/sdb2 122880 31586303 15731712 83 Linux
I'm really clueless. It would be easy to say the partition table is corrupted but then why can gparted still read it without complaints (and there are none) or how can I reconstruct the partition table from what (g)parted miraculously found out?