IOS-XE and XR are linux boxes, as are the nexus. Arista is linux based, Juniper is FreeBSD and Force10 is NetBSD (at least the older one were). Many devices in the class of enterprise or service provider grade are not going to be obtaining their addresses via DHCP and have a heavily modified version of the OS, anyway. In addition, best practices should be used in armoring the devices in this class, meaning filtering of the control plane, etc.