Show deleted partitions in use with blockdev –report

blockdev Linux command could show sector and size information for deleted partitions, which are still in use (i.e. mounted).
Deleting partitions in use their characters’ devices under /dev are preserved till the partitions are released from use and the kernel reloads the new partition table.
So before rebooting or releasing the deleted partitions blockdev may be used to report useful information for future recovery:

Delete the partitions with parted by just overwriting the partition table with empty one, for example:

[root@srv ~]# parted /dev/sda
GNU Parted 3.1
Using /dev/sda
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) p
Model: ATA Crucial_CT500MX2 (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags:

Number  Start   End     Size    Type      File system  Flags
 1      1049kB  34.3GB  34.3GB  primary                boot, raid
 2      34.4GB  34.9GB  537MB   primary                raid
 3      34.9GB  67.1GB  32.2GB  primary                raid
 4      67.1GB  500GB   433GB   extended               lba
 5      67.1GB  500GB   433GB   logical                raid
(parted) mklabel msdos
Warning: The existing disk label on /dev/sda will be destroyed and all data on this disk will be lost. Do you want to continue?
Yes/No? Yes
Error: Partition(s) 1, 2, 3, 4, 5 on /dev/sda have been written, but we have been unable to inform the kernel of the change, probably because
it/they are in use.  As a result, the old partition(s) will remain in use.  You should reboot now before making further changes.
Ignore/Cancel? Cancel
(parted) p
Model: ATA Crucial_CT500MX2 (scsi)
Disk /dev/sda: 500GB
Sector size (logical/physical): 512B/4096B
Partition Table: msdos
Disk Flags: 

Number  Start  End  Size  Type  File system  Flags

(parted) q

First, print the partition table, then delete all partitions by setting an empty new partition table!

Use blockdev to show the deleted partitions information.

[root@srv ~]# blockdev --report /dev/sda1 /dev/sda2 /dev/sda3 /dev/sda4 /dev/sdb5
RO    RA   SSZ   BSZ   StartSec            Size   Device
rw   512   512  4096       2048     34359738368   /dev/sda1
rw   512   512  4096   67110912       536870912   /dev/sda2
rw   512   512  4096   68159488     32212254720   /dev/sda3
blockdev: cannot open /dev/sda4: No such file or directory.
rw   256   512  4096  131076096    432862658560   /dev/sdb5

The partitions, which are not in use, are removed from the kernel structures, so no information is available with blockdev. Their characters’ devices under /dev/ are removed, too.

The information such as the size of the partitions and the start sectors may be used to recover the partitions manually with fdisk, sfdisk, sgdisk or parted or even testdisk – testdisk official site. In fact, testdisk is the recommended way.

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