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I'm using a linux live disk on a thinkpad laptop with a single unformatted hard drive.

lsblk is report a 0 byte block device of type disk:

# lsblk 
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
loop0    7:0    0     1G  1 loop /nix/.ro-store
sda      8:0    1  57.7G  0 disk 
├─sda1   8:1    1   1.1G  0 part /iso
└─sda2   8:2    1     3M  0 part 
sdb      8:16   1     0B  0 disk 
sdc      8:32   0 232.9G  0 disk

sda is the boot linux live disk and sdc is the laptop's hard drive. sdb should not exist.

dmesg has a few logs related to sdb:

# dmesg | grep sdb
[    7.411121] sd 3:0:0:0: [sdb] Media removed, stopped polling
[    7.411315] sd 3:0:0:0: [sdb] Attached SCSI removable disk

I can delete the device:

echo 1 > /sys/block/sde/device/delete

But it returns after a reboot. What is this block device and why does it exist?

EDIT: The computer does have an SD Card reader.

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  • Does this machine have an SD card reader or similar? Commented Aug 16, 2024 at 19:26
  • Oh actually it does have one. Would that be the cause? Commented Aug 16, 2024 at 19:33

1 Answer 1

Reset to default
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Since sdb says "Media removed" and the kernel detects it as "SCSI removable disk", it is likely this is your SD card reader.

If you put a card in it then the size for sdb should update to reflect the size of the card.

eg on my machine lsblk shows

sdc                   8:32   1     0B  0 disk

I insert an SD card in it and in sudo dmesg I see

[94255.136132] sd 4:0:0:0: [sdc] 122241024 512-byte logical blocks: (62.6 GB/58.3 GiB)
[94255.138370] sdc: detected capacity change from 0 to 122241024

And now lsblk shows

sdc                   8:32   1  58.3G  0 disk

Next I sudo eject /dev/sdc and remove the card, and now it's back to 0B output again.

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