Created attachment 9581 [details]
patch

(vanilla busybox 1.35 source)

I'm using busybox to automate the creation of a virtual machine; part of this requires me to script something like this:

#! /bin/sh
sfdisk --quiet --wipe=always --wipe-partitions=always /dev/sda << EOF
label: dos
1: type=0b, size=500M
2: type=0b, size=500M
3: type=0b, size=500M
4: type=0b, size=500M
EOF
mkdosfs /dev/sda1
mkdosfs /dev/sda2
mkdosfs /dev/sda3
mkdosfs /dev/sda4
lsblk -npr -o NAME,TYPE,UUID /dev/sda

On a "modern" machine, the problem is that without a small (>= 1s) delay between the invocations of mkdosfs, all filesystems end up with the same serial number, which is undesirable (especially if those UUIDs end up in an /etc/fstab).

Attached is a patch for consideration that attempts to use /dev/random first, falling back to the time-based mechanism in case /dev/random isn't accessible.