A switch can store up to two core images: an active and inactive. When downloading a new image, you must select on which partition to install the new image. You must install the software image to the inactive partition, and must specify that partition while downloading the image to the switch.
To find the inactive partition:
# show switch SysName: XXXXXXX SysLocation: SysContact: email@example.com, +1 888 257 3000 System MAC: 00:04:96:51:FE:E2 System Type: XXXXXXX SysHealth check: Enabled (Normal) Recovery Mode: All System Watchdog: Enabled Current Time: Thu Sep 4 00:57:18 2014 Timezone: [Auto DST Disabled] GMT Offset: 0 minutes, name is UTC. Boot Time: Wed Sep 3 20:07:11 2014 Boot Count: 402 Next Reboot: None scheduled System UpTime: 4 hours 50 minutes 7 seconds Current State: OPERATIONAL Image Selected: primary Image Booted: primary Primary ver: 188.8.131.52 Secondary ver: 184.108.40.206 Config Selected: ssh-privatekey.cfg Config Booted: ssh-privatekey.cfg ssh-privatekey.cfg Created by ExtremeXOS version 220.127.116.11 219131 bytes saved on Mon Jul 14 23:03:08 2014