The requirements to recover the operating system from a Flash drive are
Step 1 Prepare a flash drive as described in the Creating a Recovery flash drive.
Step 2 Disconnect any USB or external storage devices (including SAN storage) from the server.
Step 3 Ensure that the RAID disks are in a non-bad or non-failed state to enable proper installation.
To restore the operating system from a recovery flash drive, follow these steps:
Step 1 Power off the server in which you need to restore the operating system.
Step 2 Disconnect (unplug) the USB storage devices or any other external storage (such as SAN storage connected through a fibre channel) device that is connected to the server.
Note This ensures that only the recovery flash drive is attached to the server and prevents other storage devices from accidentally being cleared during the recovery process.
Step 3 Place the recovery flash drive in the USB port of the server and power on the server.
Step 4 When the Cisco logo appears, press the F6 key to select the boot device.
Step 5 Select the USB recovery flash drive and press Enter.
Step 6 At the boot> prompt, type one of the following options:
NoteSteps 7 and 8 are common for both Recovery and Factory options. The Recovery Options table provided below this procedure explains the options in detail.
Step 7 In the Installation method screen, choose Hard drive and select OK.
Step 8 In the Select partition screen, the partition would already be listed (for example, /dev/sda1). Select OK to start the recovery process.