CISCO IOS in a Nutshell

Using the IOS Filesystem for Images

The upgrade procedure described in the previous sections is for a Class B IOS filesystem. Class B filesystems are probably the most common, but they aren’t universal—particularly on high-end routers. There are also Class A and Class C filesystems; the filesystem you have depends on the router you’re using. Table 2-4 shows which filesystem is used in a number of different routers.

Table 2-4. Flash filesystem types

Filesystem type	Router
Class A	7000 series, C12000, and LightStream 1010
Class B	1003, 1004, 1005, 2500, 3600, 4000, AS5200, 800
Class C	3810

As far as a user is concerned, the filesystems differ primarily in the commands that they support. Table 2-5 lists the filesystem commands and what they do.

Table 2-5. Filesystem commands

Command	Filesystem	Description
cd	All	Changes the working directory.
delete	All	Deletes a file. On Class A filesystems, this command marks the file for deletion; the squeeze command purges deleted files from the filesystem. On Class B filesystems, the files disappear from directory listings (unless you use /all), but there is no way to reclaim the space, short of erasing the entire filesystem. On Class C filesystems, the file is deleted immediately.
dir	All	Displays the directory’s contents. The /all option shows deleted and undeleted files.
erase	A, B	Erases the entire filesystem.
format	A, C	Formats the filesystem.
fsck	C	Verifies the filesystem’s consistency.
mkdir ...