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Re: Taming the "lsblk" command




On Wed, Jan 09, 2019 at 06:45:22PM -0600, David Wright wrote:
So, looking at the OP, is the order of sdc a temporary state of
affairs, produced by adding partitions to sdc while sde is plugged in
and blocking the sequence? (I've never seen one letter split.)

Or is it quite normal when you reach fifteen partitions? I can
understand that the devices seem to be assigned in blocks of sixteen,
but I slightly surprised that they would be assigned in a broken
sequence when they all present at boot time.

Historically the device numbers were assigned statically:
  8 block	SCSI disk devices (0-15)
		  0 = /dev/sda		First SCSI disk whole disk
		 16 = /dev/sdb		Second SCSI disk whole disk
		 32 = /dev/sdc		Third SCSI disk whole disk
		    ...
		240 = /dev/sdp		Sixteenth SCSI disk whole disk

There was a 15 partition limit. Now you can get more, but they're assigned dynamically, outside of the historic scheme.

And surely sr0, sitting there in the middle, has a completely
different major number from sdX.

Because scsi cdroms are a completely different device type than scsi disks.