From Junos OS release 19.4R3 and later, the image size exceeds the limit supported by USB snapshot recovery due to which you cannot restore EX4300 Series devices by using this method. This article describes the details of this limitation and suggests a workaround.
After you recover an EX4300 Series device by using a external USB snapshot file and boot from the USB device, it fails to create the snapshot file in the internal disk.
Note the steps as follows and where the snapshot file creation fails.
Boot from the internal disk and take a snapshot on the USB device.
Boot up from the USB snapshot file.
Create the snapshot file in the internal disk.
Boot up from the internal disk.
*You will observe the operation fail at Step 3.
When the snapshot creation fails, you will see the error message "Not enough space to copy" in the terminal output.
test@EX4300> request system snapshot fpc0: -------------------------------------------------------------------------- Clearing current label... Partitioning internal media (/dev/da0) ... error: Not enough space to copy / (/dev/da0s2a) partition.
The reason for the snapshot to fail is that the image size is larger on newer Junos OS versions such as 19.4R3 and 20.1R1 and later versions, and the EX4300 platform is limited to handling a smaller size image snapshot. From Junos OS Release 19.4R3, the image size exceeds the limit supported by USB snapshot recovery.
Workaround
As a workaround, use the general USB recovery method as shown below rather than the snapshot method on later Junos OS versions.
Copy the directories below. Note that you can select the necessary files to save.
-/config/ *Config files -/var/home/ *User files -/var/log/ *Log files -/var/tmp/ *Temporary files -/var/db/scripts *JUNOScript files
Refer to KB20643 - [EX] Performing and resolving any common issues during Format Install on legacy EX platforms [juniper.net] for USB recovery.
After the EX device boots up, restore the copied files.
2022-09-17: KB created