Understanding System Snapshot on EX Series Switches

You can create copies of the software running a Juniper Networks EX Series Ethernet Switch using the system snapshot feature. The system snapshot feature takes a “snapshot” of the files currently used to run the switch and copies them to an alternate storage location. You can then use this snapshot to boot the switch at the next bootup or as a backup boot option.

The switch can boot from either internal flash media or external (USB) flash media. The contents of the snapshot vary depending on whether you create the snapshot on the media that the switch booted from or on the media that it did not boot from:

Snapshots are particularly useful for moving files onto USB flash drives. You cannot use the copy command or any other file-moving technique to move files from an internal memory source to USB memory on the switch.

• If you create the snapshot on the media that the switch did not boot from, the following partitions on the boot media are included in the snapshot: root, altroot, var, var/tmp, config.

  The root partition is the primary boot partition, and the altroot partition is the backup boot partition.

• If you create the snapshot on the media that the switch booted from, the root partition that the switch booted from is copied to the alternate root partition. The var, var/tmp, and config partitions are not copied as part of the snapshot because they already exist on the boot media.

The system snapshot feature has the following limitations:

• You cannot use snapshots to move files to any destination outside the switch other than an installed external USB flash drive or switches that are members of the same Virtual Chassis as the switch on which you created the snapshot..
• Snapshot commands, like all commands executed on a Virtual Chassis, are executed on the local member switch. If different member switches request the snapshot, the snapshot command is pushed to the Virtual Chasis member creating the snapshot and is executed on that member, and the output is then returned to the switch that initiated the process. For instance, if the command to create an external snapshot on member 3 is entered on member 1, the snapshot of internal memory on member 3 is taken on external memory on member 3. The output of the process is seen on member 1. No files move between the switches.