Filling a device with random data

Hey there :)

Section 2.19 of the [FAQ][1] explains how to fill devices with random data using dm-crypt: cryptsetup opens a plain mapping, zeros are written to it and it is closed. If LUKS is set up on the device afterwards, this translates to the following commands:

```
cryptsetup open --type=plain --key-file=/dev/urandom -- /dev/foo temporary
dd if=/dev/zero of=/dev/mapper/temporary
cryptsetup close -- temporary
cryptsetup luksFormat -- /dev/foo
cryptsetup open -- /dev/foo bar
# mkfs / pvcreate -- /dev/mapper/bar
```

I would like to skip the first mapping and shorten the procedure as follows:

```
cryptsetup luksFormat -- /dev/foo
cryptsetup open -- /dev/foo bar
dd if=/dev/zero of=/dev/mapper/bar
# mkfs / pvcreate -- /dev/mapper/bar
```

Does filling a device with random data under a separate dm-crypt mapping offer any security benefit?

Kind regards,

David J. Shourabi Porcel


[1]: https://gitlab.com/cryptsetup/cryptsetup/-/wikis/FrequentlyAskedQuestions