Safely upgrading an IOS image (IOS 15.0x used as Example)

Easy as pie! Using a recent upgrade to 15.0(1)SE2 as an example.

Prepare for the upgrade: 

+ Identify the image feature set needed: run the command # show version
+ Navigate to the Cisco Software Download site and download the needed image.
+ Place the new 15.0(1)SE2 IOS image (.bin file) on your  FTP/ TFTP server, make sure the switch has access to the server (ping sourcing from the TFTP interface).

+ Have the original image also available on the TFTP server  (better safe than sorry no?)

+ Ensure there is console access to the switch that will be upgraded.  If you have a neighboring device – you can setup console access by connecting to the console port from the aux port of the neighboring device and use a very useful reverse telnet

+ Backup the configuration
# copy startup-config tftp
!–Enter IP address, press enter
!–Confirm filename, press enter

+ Check the amount of free memory using the command.
# dir flash:

If there is not enough space, delete the old image – make sure there is a backup of the image.
# Delete flash:c3560-old-imagename-example.bin
!– to dete a directory, # delete /force /recursive {directoryName}
If there is enough free space, copy the image to flash.

Executing the Upgrade

# copy tftp flash:
!– Enter IP address, press enter
!– Confirm Source file name, press enter
!– Confirm destination file name. Press enter.
!– You will see many !!!!! during load.

Confirm the new image is available:
# dir flash:

Verify the checksum
# verify flash:c3560-new-imagename-example.bin
!– If you get an error, the image may have corrupted during transfer.

Set the boot statement to the new image
# config t
(config)# boot system flash:c3560-new-imagename-example.bin

Verify the boot statement
# show boot

Save the configuration
# copy run start
# write memory

Reload the device
# reload

Verify new code is applied
#show ver

Rollback Plan 
Change the boot statement to the original image. Reload.


And that’s all folks!

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