error: external media missing or invalid is seen while validating system snapshots on EX4300 Juniper Networks devices.

The following error can be seen: "error: external media missing or invalid" while validating system snapshots on EX4300 Juniper Networks devices.

root@switch> show system snapshot

fpc0:

--------------------------------------------------

error: external media missing or invalid

The error is seen since that command is validating system snapshots on external media, such as USB drive. All the Legacy EX switches have supported resilient dual-root partition (RPS) features where the EX file system was formatted with a primary and backup root partition.

EX switches are shipped from the factory with identical Junos OS images in slice/partition 1 and 2 so that if the switch fails to boot from the active root partition due to file system corruption, the built-in resiliency will ensure that the EX switch automatically boots from the alternate root partition. On an existing EX platform with RPS, the boot loader detects Junos OS boot failure based on the ‘boot success’ indication set by Junos on successful boot, and switches to the alternate partition.

On EX4300 switches:

"request system snapshot slice alternate" is used to take a snapshot of the files currently used to run the switch and copy them to the alternate root partition residing on the internal flash media.

"request system reboot slice alternate" is used to reboot the switch from the alternate root partition. [Optional]

show system snapshot media internal is used to display snapshot information from the primary and backup root partition.