思科交换机分为两种系统，分别是IOS和CatOS，下面介绍IOS版本的操作，
Switch#write erase
Erasing the nvram filesystem will remove all files! Continue? [confirm]y[OK]
Erase of nvram: complete
Swtich# delete flash:vlan.dat ------------老版本需做此操作。
Delete filename [vlan.dat]?
Delete flash:vlan.dat? [confirm]y
Switch#reload
System configuration has been modified. Save? [yes/no]: no
Proceed with reload? [confirm]
另一种方法是启动的时候按Mode进入引导模式，执行如下命令：
flash_init
rename flash:config.text flash:config.old
boot