Cisco使用的操作系统称为IOS——Internetworking Operating System，存储在Cisco设备的Flash存储器上，除了IOS外，还有一个重要的文件：设备配置文件。为了方便管理，我们可以把IOS系统及设备配置文件备份在本地计算机上，当出故障时，我们可以把IOS系统或配置文件恢复到Cisco设备上，本文的操作以Cisco 3550为例。
⑴pwd命令，显示当前路径。
SW3550#pwd
flash:
SW3550#pwd
flash:/c3550-ipservices-mz.122-25.SEE/
⑵cd命令，切换目录命令
SW3550#cd c3550-ipservices-mz.122-25.SEE
⑶dir，显示当前路径下的文件
SW3550#dir
Directory of flash:/
2 -rwx 616 Mar 1 1993 01:25:31 +00:00 vlan.dat
4 drwx 128 Mar 1 1993 01:17:39 +00:00 c3550-ipservices-mz.122-25.SEE
3 -rwx 3977 Mar 1 1993 02:20:42 +00:00 config.old
371 -rwx 2356 Mar 1 1993 03:08:11 +00:00 config.text
15998976 bytes total (8002560 bytes free)
SW3550#
show flash命令也可以显示flash闪存中存储的文件：
SW3550#show flash
Directory of flash:/
2 -rwx 616 Mar 1 1993 01:25:31 +00:00 vlan.dat
4 drwx 128 Mar 1 1993 01:17:39 +00:00 c3550-ipservices-mz.122-25.SEE
3 -rwx 3977 Mar 1 1993 02:20:42 +00:00 config.old
371 -rwx 2356 Mar 1 1993 03:08:11 +00:00 config.text
15998976 bytes total (8002560 bytes free)
SW3550#
dir all用来显示当前路径下所有的文件
SW3550#dir all
Directory of flash:/
2 -rwx 616 Mar 1 1993 01:25:31 +00:00 vlan.dat
4 drwx 128 Mar 1 1993 01:17:39 +00:00 c3550-ipservices-mz.122-25
.SEE
3 -rwx 3977 Mar 1 1993 02:20:42 +00:00 config.old
371 -rwx 2356 Mar 1 1993 03:08:11 +00:00 config.text
15998976 bytes total (8002560 bytes free)
Directory of zflash:/
2 -rwx 616 Mar 1 1993 01:25:31 +00:00 vlan.dat
4 drwx 128 Mar 1 1993 01:17:39 +00:00 c3550-ipservices-mz.122-25
.SEE
3 -rwx 3977 Mar 1 1993 02:20:42 +00:00 config.old
371 -rwx 2356 Mar 1 1993 03:08:11 +00:00 config.text
15998976 bytes total (8002560 bytes free)
Directory of system:/
3 dr-x 0 <no date> memory
1 -rw- 2376 <no date> running-config
2 dr-x 0 <no date> vfiles
No space information available
Directory of nvram:/
380 -rw- 2356 <no date> startup-config
381 ---- 0 <no date> private-config
393216 bytes total (390808 bytes free)
Cisco 3550的IOS文件扩展名是.bin，全名是：c3550-ipservices-mz.122-25.SEE.bin，存储在flash下的c3550-ipservices-mz.122-25.SEE目录下。
SW3550#cd c3550-ipservices-mz.122-25.SEE
SW3550#dir
Directory of flash:/c3550-ipservices-mz.122-25.SEE/
5 -rwx 6410981 Mar 1 1993 01:17:39 +00:00 c3550-ipservices-mz.122-25
.SEE.bin
6 drwx 4160 Mar 1 1993 01:17:59 +00:00 html
15998976 bytes total (8002560 bytes free)
⑷copy命令备份IOS及配置文件
首先使用Cisco TFTP server架设一台TFTP服务器：
图一 Cisco TFTP Server
使用copty flash tftp命令把flash存储器内的IOS文件备份到TFTP Server上。
SW3550#copy flash tftp
Source filename [/c3550-ipservices-mz.122-25.SEE/c3550-ipservices-mz.122-25]? c3
550-ipservices-mz.122-25.SEE.bin //输入IOS的路径及文件
Address or name of remote host []? 192.168.1.107 //输入TFTP Server的IP地址
Destination filename [c3550-ipservices-mz.122-25.SEE.bin]? //输入备份的目的址，也可以使用默认的名称。
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
6410981 bytes copied in 53.516 secs (119796 bytes/sec)
使用copy startup-config tftp命令把配置文件备份到TFTP Server上。
SW3550#copy startup-config tftp
Address or name of remote host []? 192.168.1.107
Destination filename [sw3550-confg]? sw3550startupBack
!!
2356 bytes copied in 0.044 secs (53545 bytes/sec)
SW3550#
使用copty tftp startup-config把TFTP上存储的配置文件备文件恢复到交换机上：
SW3550#copy tftp startup-config
Address or name of remote host []? 192.168.1.107
Source filename []? sw3550startupBack
Destination filename [startup-config]?
Accessing tftp://192.168.1.107/sw3550startupBack...
Loading sw3550startupBack from 192.168.1.107 (via Vlan1): !
[OK - 2356 bytes]
[OK]
2356 bytes copied in 9.196 secs (256 bytes/sec)
⑸erase命令删除配置文件，慎用该命令！
SW3550#erase startup-config
Erasing the nvram filesystem will remove all configuration files! Continue? [con
firm]y[OK]
Erase of nvram: complete
SW3550#
02:01:36: %SYS-7-NV_BLOCK_INIT: Initalized the geometry of nvram
删除了startup-config文件后，查看NVRAM(非易失内存)，可以看到startup-config文件大小为0byte。
Directory of nvram:/
382 -rw- 0 <no date> startup-config
383 ---- 0 <no date> private-config
393216 bytes total (393164 bytes free)
恢复完配置文件后，再查看NVRAM：
Directory of nvram:/
380 -rw- 2356 <no date> startup-config
381 ---- 0 <no date> private-config
393216 bytes total (390808 bytes free)
本文只是简单地介绍了dir、cd、copy、erase等命令的使用，可以完成一些重要的管理工具。