#!/bin/sh
hostnames()
{
cat <<EOF
adam
billy
cletus
doris
elaine
frank
gilbert
hilda
EOF
}

next_hostname()
{
    h=$(hostname) || exit
    hostnames | sed -n "/^${h}\$/ {n;p;q}" || exit
}

set -x
hostname=$(next_hostname)
[ "$hostname" ] || hostname=$(hostnames | head -n1)
printf '%s\n' "$hostname" > /etc/hostname
sed -i -e 's/\blocalhost\b/& '"$hostname"'/' /etc/hosts