Junos OS
The Junos operating system (Junos OS) used in Juniper Networks network devices creates an environment for accelerating the deployment of services and applications over a single network.

One Operating System 
Unlike other network operating systems that share a common name but splinter into many different programs, Junos OS is a single, cohesive operating system that is shared across all network devices and product lines. Junos OS allows Juniper Networks engineers to develop software features once and share these features across all product lines simultaneously, thus reducing the training for each product and interoperability in production environments.

CLI
The Junos OS CLI is a text-based command interface for configuring, troubleshooting, and monitoring the Juniper device and network traffic associated with it. It supports two types of command modes.
 Operational Mode—Monitors hardware status and displays information about network data that passes through or into the hardware.
 Configuration Mode—Configures the Juniper router, switch, or security device, by adding, deleting, or modifying statements in the configuration hierarchy.

FIPS 140-2 Security Compliance
For advanced network security, a special version of Junos OS called Junos-FIPS 140-2 Security Compliance is available, providing customers with software tools to configure a network of Juniper Networks devices in a Federal Information Processing Standards (FIPS) environment.

Juniper Extension Toolkit (JET)
Junos OS offers programming interfaces and the Juniper Extension Toolkit (JET) for developing applications that unlock more value from the network. JET is a standard component of Junos OS, and it runs on all Juniper routers, switches, and security devices. JET simplifies the automation of operational, configuration, and management tasks, providing a rich set of open and customizable APIs for control, management, and data planes. It supports standardized programming languages for application development and communication to the Junos OS fast programmable database through standardized and open data exchange formats. It also opens up Trio and Express ASICs via a set of third-party controller-specific adapters, including SAI, OpenFlow, and P4.

Junos Fusion
Junos Fusion helps reduce network complexity and operational expenses by enabling multiple distributed devices to be managed as a single, logical device. Two different Junos Fusion architectures are available, one for provider edge and one for enterprise.

Junos Node Slicing
Node slicing is a Junos OS feature that enables creating multiple partitions from a single physical MX Series router. Each partition behaves as an independent router, with its own dedicated control plane, data plane, and management plane, allowing it to run multiple services on a single physical router.

Routing Protocols and Applications
Junos OS supports a variety of routing protocols and applications. It also supports class of service (CoS), Ethernet VPN (EVPN), firewall filters and policers, flow monitoring, and Layer 2 features. It's a flexible routing policy language that is used for controlling route advertisements and path selection. Junos OS generally adheres to industry standards for routing and Multiprotocol Label Switching (MPLS). The Junos OS supports high availability mechanisms that are not standard to Unix, such as graceful restart.

Secure Boot
Secure boot is a significant system security enhancement based on the UEFI standard. It works by safeguarding the BIOS itself from tampering or modification and then maintaining that protection throughout the boot process. The secure boot process begins with secure flash, which ensures that unauthorized changes cannot be made to the firmware. Authorized releases of Junos OS carry a digital signature produced by either Juniper Networks directly or one of its authorized partners.

Architecture
Junos OS has two different architecture variations: 
 Junos OS is based on the FreeBSD operating system and can run as a guest virtual machine on a Linux VM host. 
 Junos OS Evolved is based on the Linux operating system, and provides direct access to Linux utilities and operations. 
Both operating systems use the same command-line interface (CLI) user interface, the same applications and features, and the same management and automation tools—but Junos OS Evolved infrastructure has been entirely modernized to enable higher availability, accelerated deployment, greater innovation, and improved operational efficiencies.

References

External links 
 
 Juniper Networks to Use Oracle Berkeley DB in JUNOS Software

Computer networking
Embedded operating systems
FreeBSD
Juniper Networks
Network operating systems
1998 software