IOS 7.0.120.0升7.6.120.0,按正常的流程是可以直接升级的，但此次升级碰到了问题。7.6的IOS刷进FLASH之后，系统提示 Reboot。重启后选择7.6.120.0进入系统，但系统一直停留在（启动镜像）这个阶段，无法启动，如下所示。
WLCNG Boot Loader Version 1.0.16 (Built on Feb 28 2011 at 13:14:54 by cisco)
Board Revision 0.0 (SN: PSZ16440A3A, Type: AIR-CT2504-K9) (W)
Verifying boot loader integrity... OK.
OCTEON CN5230C-SCP pass 2.0, Core clock: 750 MHz, DDR clock: 330 MHz (660 Mhz data rate)
CPU Cores: 4
DRAM: 1024 MB
Flash: 32 MB
Clearing DRAM........ done
Network: octeth0', octeth1, octeth2, octeth3
' - Active interface
E - Environment MAC address override
CF Bus 0 (IDE): OK
IDE device 0:
- Model: 1GB CompactFlash Card Firm: CF B612J Ser#: A191105254A12j5C7VDr
- Type: Hard Disk
- Capacity: 977.4 MB = 0.9 GB (2001888 x 512)
Press now to access the Boot Menu...
Loading primary image (7.6.120.0)
100%
36933676 bytes read
Launching...
Launching images...-----系统一直停留在这里，无法继续启动
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后来以为7.6.120.0 IOS校验有问题，就把backup的IOS升到了7.6.130.0，结果也是到了这一步启动镜像就像死机一样，造成Active和Backup镜像都启动不了。后来重启按ESC进入boot menu，选择代码6。
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Boot Loader Menu
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1. Run primary image (7.6.130.0) - Active
2. Run backup image (Bad image type)
3. Change active boot image
4. Clear configuration
5. Format FLASH Drive
6. Manually update images
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Enter selection: 6
Launching...
Launching images...
init started: BusyBox v1.6.0 (2010-05-13 17:50:10 EDT) multi-call binary
Mount failed for selinuxfs on /selinux: No such file or directory
starting pid 655, tty '': '/etc/init.d/rcS'
Use DHCP for ip configuration (Y/n)? n
Enter switch IP address: 10.40.3.2----------WLC Management IP地址
Enter switch netmask: 255.255.255.0------子网掩码
Enter switch gateway: 10.40.3.1-------------该网段的网关地址
Enter TFTP server IP address: 10.40.3.3---TFTP服务器IP
You have entered:
IP Address : 10.40.3.2
Netmask : 255.255.255.0
Gateway : 10.40.3.1
Server Ip Addr : 10.40.3.3
Is this correct(y/N)? y
!!! WARNING updating using .aes or unapproved files will disable this unit !!!
Do you want to update RTOS (y/N)? y
Do you want to update Primary Or Secondary Image (P/s)? s
Enter filename for RTOS update: @注：由于第一次升级时这里填写了WLC的IOS文件，所以导致了上文中的第二个镜像是:Bad image type,这里正确的文件名应该是：AS_5500_RTOS-7.0.116.0
Enter filename for FP update:
注：这里的两个文件是WLC底层的固件，需要CISCO提供，后来Cisco TAC张国敏张老师分享了这个WLC底层固件，恢复了WLC，重新进入了7.0.220.0。系统恢复之后，尝试升级到7.4.120.0，还是遇到了同样的问题。最后只能返厂维修了。
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