Systemd unique hostname

hostnamegen.service

[Unit]
Description=Generate Unique Hostname
DefaultDependencies=no
Wants=local-fs.target swap.target network-pre.target
After=local-fs.target swap.target
Before=network-pre.target
ConditionPathExists=!/etc/hostname
ConditionPathExists=!/boot/hostname

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/bin/sh -c 'echo "rpi-$$(head /dev/urandom | tr -dc 0-9A-Z | head -c 6)" > /etc/hostname && /bin/hostname -F /etc/hostname'
TimeoutSec=30s

[Install]
WantedBy=network.target