Juniper EX4200 USB Software Upgrade

I had to add a Juniper EX4200 switch to a stack today which already had 8 switches in it.
There are a few criteria which Juniper specify for adding a new switch to a stack.

1. You can have up to 10 switches in a Virtual Chassis
2. The Software image of the new switch must match the version on the master

This is where my first problem started, having checked the version of the current master and the new switch they were different!
Current master switch was running 10.4R5.5 and the new switch was running the latest 11 image.

So I had to downgrade the new switch to 10.4R5.5 – the simplest and safest way to do this is to with the switch still standalone and with the image on a USB Key.  Here are the steps.

1. Download your image from Juniper.net and put in the root of a FAT32 formatted USB Key
2. Insert the USB key into the back of the EX4200 and boot the switch
3. You then need to mount the usb key

root@:RE:0% mount_msdosfs /dev/da1s1 /mnt

Once the USB has been mounted you can run the request system software add command

root> request system software add  /mnt/jinstall-ex-4200-10.4R5.5-domestic-signed.tgz

You now have to be patient as this process takes a few minutes, once the image has been loaded you will be asked to reboot.

Checking pending install on fpc0
Validating on fpc0
Done with validate on all virtual chassis members
fpc0:
WARNING: A reboot is required to install the software
WARNING:     Use the ‘request system reboot’ command immediately

root@:RE:0% cli
{master:0}
root> request system reboot
Reboot the system ? [yes,no] (no) yes
*** FINAL System shutdown message from root@ ***                             
System going down IMMEDIATELY 

Once the switch has rebooted a show version will show the switch is now running the 10 Image

root> show version
fpc0:
————————————————————————–
Model: ex4200-48p
JUNOS Base OS boot [10.4R5.5]
JUNOS Base OS Software Suite [10.4R5.5]
JUNOS Kernel Software Suite [10.4R5.5]
JUNOS Crypto Software Suite [10.4R5.5]
JUNOS Online Documentation [10.4R5.5]
JUNOS Enterprise Software Suite [10.4R5.5]
JUNOS Packet Forwarding Engine Enterprise Software Suite [10.4R5.5]
JUNOS Routing Software Suite [10.4R5.5]
JUNOS Web Management [10.4R5.5]