Linux – How does udev get device numbers for the devices it creates

devtmpfs is a file system with automated device nodes populated by the kernel. This means you don't have to have udev running nor to create a static /dev layout with additional, unneeded and not present device nodes. Instead the kernel populates the appropriate information based on the known devices.

On the other hand the standard /dev handling requires either udev, an additional daemon running or to statically create device nodes on /dev.

This is untested in combination:

Add a udev rule to IMPORT{program}="/usr/local/sbin/unique-num /run/miner-counter 0 MINER_NUM" for your miners.

Then you could use a simple shell script, something like this somewhat tested program:

#!/bin/sh

if [ $# -ne 3 ]; then
    echo "Usage: $0 data-file initial var-name" >&2
    exit 1
fi

datfile="$1"
lockfile="$1.lck"
initial=$2
key="$3"

(
    flock -x 9
    num=$initial
    if [ -e "$datfile" ]; then
        read -r num < "$datfile"
    fi

    next=`expr $num + 1`;
    echo $next > "$datfile"

    echo "$key=$num"
) 9> "$lockfile"

Then you can use that udev environment variable to name your miners.