Managing the Cisco File System / IOS file system overview

Managing the Cisco File System

IOS file system overview

5.2.1

This page will introduce the Cisco IOS File System.
Routers and switches depend on software for their operation. The two types of software required are operating systems and configuration.
The operating system used in almost all Cisco devices is the Cisco IOS. The Cisco IOS is the software that allows the hardware to function as a router or switch. The IOS file is several megabytes.
The software a router or switch uses is referred to as the configuration file or the config. The configuration contains the instructions that define how the device is to route or switch. A network administrator creates a configuration that defines the desired functionality of a Cisco device. The functions that can be specified by the configuration are the IP addresses of the interfaces, routing protocols, and networks to be advertised. The configuration file typically is a few hundred to a few thousand bytes.
Each of the software components is stored in memory as a separate file. These files are also stored in different types of memory. 
The IOS is stored in a memory area called flash. Flash memory provides non-volatile storage of an IOS that can be used as an operating system at startup. The flash allows the IOS to be upgraded or stores multiple IOS files. In many router architectures, the IOS is copied into and run from RAM.
A copy of the configuration file is stored in NVRAM to be used during startup. This is referred to as the startup configuration or startup config. The configuration in RAM is used to operate a router. It is referred to as the running configuration or running config.
Version 12 and later releases of the IOS provide a single interface to all the file systems that a router uses. This is referred to as the Cisco IOS File System (IFS). The IFS provides a single method to perform all the file system management for a router. This includes the flash memory file systems, the network file systems, such as TFTP and FTP, and read or write data, such as NVRAM, the running configuration, and ROM. The IFS uses a common set of prefixes to specify file system devices. 
The IFS uses the URL convention to specify files on network devices and the network. The URL convention identifies the location of the configuration files following the colon as [[[//location]/directory]/filename]. The IFS also supports FTP file transfers.
The Interactive Media Activity will help students become familiar with the IFS configuration files and their locations.
The next page will describe the IOS naming conventions.