1. Download the relevant files kickstart and system file

2. Copy the files via TFTP to bootflash
Nexus5548# copy tftp://10.0.1.227/n5000-uk9-kickstart.5.1.3.N1.1.bin bootflash:n5000-uk9-kickstart.5.1.3.N1.1.bin
Nexus5548# copy tftp://10.0.1.227/n5000-uk9.5.1.3.N1.1.bin bootflash:n5000-uk9.5.1.3.N1.1.bin
3. Use the install command for the new image

Nexus5548-2# install all kickstart bootflash:n5000-uk9-kickstart.5.1.3.N1.1.bin system bootflash:n5000-uk9.5.1.3.N1.1.bin
Verifying image bootflash:/n5000-uk9-kickstart.5.1.3.N1.1.bin for boot variable "kickstart".
[####################] 100% -- SUCCESS
Verifying image bootflash:/n5000-uk9.5.1.3.N1.1.bin for boot variable "system".
[####################] 100% -- SUCCESS
Verifying image type.
[####################] 100% -- SUCCESS
Extracting "system" version from image bootflash:/n5000-uk9.5.1.3.N1.1.bin.
[####################] 100% -- SUCCESS
Extracting "kickstart" version from image bootflash:/n5000-uk9-kickstart.5.1.3.N1.1.bin.
[####################] 100% -- SUCCESS
Extracting "bios" version from image bootflash:/n5000-uk9.5.1.3.N1.1.bin.
[####################] 100% -- SUCCESS
Performing module support checks.
[####################] 100% -- SUCCESS
Notifying services about system upgrade.
[####################] 100% -- SUCCESS
Compatibility check is done:
Module  bootable          Impact  Install-type  Reason
------  --------  --------------  ------------  ------
     1       yes      disruptive         reset  Non-disruptive install not supported if L3 was enabled
Images will be upgraded according to following table:
Module       Image         Running-Version             New-Version  Upg-Required
------  ----------  ----------------------  ----------------------  ------------
     1      system            5.0(3)N1(1b)             5.1(3)N1(1)           yes
     1   kickstart            5.0(3)N1(1b)             5.1(3)N1(1)           yes
     1        bios      v3.5.0(02/03/2011)      v3.5.0(02/03/2011)            no
     1      SFP-uC                v1.0.0.0                v1.0.0.0            no
     1   power-seq                    v1.0                    v1.0            no
     3   power-seq                    v5.0                    v5.0            no
     1          uC                v1.2.0.1                v1.2.0.1            no
Switch will be reloaded for disruptive upgrade.
Do you want to continue with the installation (y/n)?  [n] y
Install is in progress, please wait.
Performing runtime checks.
[####################] 100% -- SUCCESS
Setting boot variables.
[####################] 100% -- SUCCESS
Performing configuration copy.
[####################] 100%


4. After the reboot login again and verify the version

Nexus5548# sh ver
Cisco Nexus Operating System (NX-OS) Software
TAC support: http://www.cisco.com/tac
Documents: http://www.cisco.com/en/US/products/ps9372/tsd_products_support_serie
s_home.html
Copyright (c) 2002-2011, Cisco Systems, Inc. All rights reserved.
The copyrights to certain works contained herein are owned by
other third parties and are used and distributed under license.
Some parts of this software are covered under the GNU Public
License. A copy of the license is available at
http://www.gnu.org/licenses/gpl.html.
Software
  BIOS:      version 3.5.0
  loader:    version N/A
  kickstart: version 5.1(3)N1(1)
  system:    version 5.1(3)N1(1)
  power-seq: Module 1: version v1.0
  uC:        version v1.2.0.1
  SFP uC:    Module 1: v1.0.0.0
  BIOS compile time:       02/03/2011
  kickstart image file is: bootflash:///n5000-uk9-kickstart.5.1.3.N1.1.bin
  kickstart compile time:  12/6/2011 22:00:00 [12/07/2011 06:30:01]
  system image file is:    bootflash:///n5000-uk9.5.1.3.N1.1.bin
  system compile time:     12/6/2011 22:00:00 [12/07/2011 08:09:44]
Hardware
  cisco Nexus5548 Chassis ("O2 32X10GE/Modular Universal Platform Supervisor")
  Intel(R) Xeon(R) CPU         with 8263872 kB of memory.
  Processor Board ID JAF1515BBRA
  Device name: Nexus5548-2
  bootflash:    2007040 kB
Kernel uptime is 0 day(s), 0 hour(s), 3 minute(s), 13 second(s)
Last reset at 720106 usecs after  Thu Dec 15 20:15:10 2011
  Reason: Disruptive upgrade
  System version: 5.0(3)N1(1b)
  Service:
plugin
  Core Plugin, Ethernet Plugin