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Back up and Recover Software with Snapshots

SUMMARY The installation process removes all stored files on the device except for files such as the juniper.conf, SNMP ifIndexes, and SSH files. Therefore, you should back up your current configuration in case you need to return to the current software installation after running the installation program. You can also recover the configuration file and the Junos OS Evolved software, if required.

Understand Snapshots

You create copies of both the software and the configuration running on a device using the request system snapshot command. The request system snapshot command takes a “snapshot” of the files currently used to run the device and copies the files onto the alternate solid-state drive (SSD). The snapshot contains the complete contents of the /soft, /config, and /root directories, which include the current and all rollback software images, copies of user data, the active configuration, the rescue configuration, and content from the /var directory (except the /var/core, /var/external, /var/log, and /var/tmp directories). You can then use this snapshot to boot the device at the next boot up or as a backup boot option.

Note:

We recommend that you take a snapshot after every software upgrade or downgrade.

System snapshots have the following limitations:

  • You cannot use snapshots to move files to any destination outside of the device, including an installed external USB flash drive.

  • Snapshot commands always run on a local Routing Engine and snapshot to the secondary SSD on the local Routing Engine.

Restoring from a snapshot is especially effective as a boot-up option after a disk corruption, as it is the only recovery option that allows you to completely restore the software and configuration in the event of a corrupted disk.

After an upgrade, if the installation fails during early boot, the Routing Engine automatically reverts to booting from the secondary SSD, where snapshots are stored. You can then reboot the Routing Engine using the snapshot saved on the secondary SSD.

Create a Snapshot on the Secondary SSD and Use It to Recover the Software Installation

To create a snapshot on the secondary SSD (/dev/sdb) of the primary (or only) Routing Engine:

  1. Issue the request system snapshot operational mode command.
  2. Use the show system snapshot operational mode command to see the snapshot images available on the Routing Engines.
  3. To recover the primary Routing Engine using the snapshot, boot the Routing Engine from the secondary SSD (disk2).
  4. If the Routing Engine has successfully booted from the secondary SSD, after the Routing Engine boots up, you see a message similar to the following before the login prompt: