proxmox-backup/etc/proxmox-backup.service.in

[Unit]
Description=Proxmox Backup API Server
Wants=network-online.target
After=network.target

[Service]
Type=simple
ExecStart=%LIBEXECDIR%/proxmox-backup/proxmox-backup-api
Restart=on-failure

[Install]
WantedBy=multi-user.target