Non-interactive user create & password change for Alpine Linux

alpine_password.sh

#! /usr/bin/env sh
# Create unprivileged Alpine linux user. Run this script as root/sudo

# Don't prompt for password and make group same as username, default path & shell

adduser -D -g appuser appuser

# Set a decent random password (aiming for a 256 bit security level, but better than "monkey")
PW=$(head -c 32 /dev/urandom | base64) && echo -e "$PW\n$PW" | passwd appuser && unset PW

# Alternatively, to echo: PW=$(head -c 32 /dev/urandom | base64) && echo -e "$PW\n$PW" | tee  /dev/stderr | passwd appuser && unset PW

# Results in something like this
#  /etc/password: appuser:x:1000:1000:appuser:/home/appuser:/bin/ash
#  /etc/shadow:   appuser:$6$M2LLoqMEfhFOc3Qe$W.FOl61we8PIte.KDMWxifg/TVdFgPKdIuMDISH74laCtA7t3OorjOiGPLdGPbTizczPUu17EaXoH32hu1OKo1:19088:0:99999:7:::

# To revert: deluser --remove-home appuser