Given a block device, how can I get its "parent"?
A example would be a LUKS virtual decrypted device (/dev/mapper/decrypted), whose parent would be the encrypted block device (/dev/sdb)
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1 Answer
For non-interactive work, this can be done using dmsetup deps, which lists the block device's dependencies. By default, it'll return the major:minor device numbers, but you can provide additional options to output a name:
dmsetup deps -o devname /dev/mapper/decrypted
For doing this interactively, the best way is just to use lsblk, which outputs a nicely formatted graph:
└─sda8 8:8 0 43.9G 0 part
└─sda8_crypt 253:2 0 43.9G 0 crypt
├─vgpersonal-home 253:3 0 83G 0 lvm
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I think the output of
dmsetup depsis not very complete: For example when I specify a logical volume, I just get the name of the disk partition (likesda8). Is there a command to get all parents, children, and siblings? Re-using dmsetup does not work: For exampledmsetup deps -o devname /dev/sda8falsely claimsDevice sda8 not found. Of course it exists!U. Windl– U. Windl2018-11-20 12:36:42 +00:00Commented Nov 20, 2018 at 12:36 -
@U.Windl
/dev/sda8is very likely representing hardware, not a devicemapper blockdevice, sodmsetupcan't possibly work there (as it states, the device doesn't exist, as far as devicemapper is concerned). Did you try usinglsblk, which I mentioned in the answer?loopbackbee– loopbackbee2018-11-25 20:33:33 +00:00Commented Nov 25, 2018 at 20:33 -
In my view sda8 is not actual hardware, but sda would be: Without an sda, there would not be an sda8, so sda8 is a child of sda, and sda is a parent of sda8.U. Windl– U. Windl2018-11-27 07:47:27 +00:00Commented Nov 27, 2018 at 7:47
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@U.Windl And that's exactly what you get with
lsblk:)loopbackbee– loopbackbee2018-11-28 00:00:22 +00:00Commented Nov 28, 2018 at 0:00