Booting an EX Series Switch Using a Software Package Stored
on a USB Flash Drive

There are two methods of getting Junos OS onto a USB
flash drive before using the software to boot the switch. You can
pre-install the software onto the USB flash drive before inserting
the USB flash drive into the USB port, or you can use the system snapshot
feature to copy files from internal switch memory to the USB flash
drive.

To move files into USB flash memory using a system snapshot
and use those files to boot the switch, see Creating a Snapshot and Using It to Boot an EX Series Switch. We recommend that you use this method to boot the switch from a
USB flash drive if your switch is running properly.

If you need to pre-install the software onto the USB flash drive,
you can use the method described in this topic. Pre-installing the
Junos OS onto a USB flash drive to boot the switch can be done at
any time and is particularly useful when the switch boots to the loader
prompt because the switch cannot locate the Junos OS in internal flash
memory.

Ensure that you have the following tools and parts
available to boot the switch from a USB flash drive:

• A USB flash drive that meets the EX Series switch USB
  port specifications. See USB Port Specifications for an EX Series Switch.
• A computer or other device that you can use to download
  the software package from the Internet and copy it to the USB flash
  drive.

To download a Junos OS package onto a USB flash drive
before inserting the USB flash drive:

1. Download the Junos OS package that you would
   like to place onto the EX Series switch from the Internet onto the
   USB flash drive using your computer or other device. See Downloading Software Packages from Juniper Networks.
2. Remove the USB flash drive from the computer or
   other device.
3. Insert the USB flash drive into the USB port on
   the switch.
4. This step can only be performed when the prompt
   for the loader script (loader>) is displayed. The loader
   script starts when the Junos OS loads but the CLI is not working for
   any reason or if the switch has no software installed.

   Install the software package onto the switch:

   loader> install source

   where source represents the name and location of the Junos OS package on
   the USB flash drive. The Junos OS package on a flash drive is commonly
   stored in the root drive as the only file—for example, file:///jinstall-ex-4200-9.4R1.5-domestic-signed.tgz.