How to update the rollback config and OS on the backup or /altroot partition on SRX

This article summarizes how to update the roll back configuration and OS on the backup partition (/altroot) on Junos devices running version 10.0 and higher image.

To update OS and configurations saved on the backup partition of dual root device, use the “request system snapshot slice alternate” command.

Starting with Junos version 10.0, SRX and J series routers have two roots on the system. These are identical in terms of functionality and each root can store only one Junos image. At any point of time, either partition 1 or partition 2 will be the primary and the other one will be the backup. The role of these partitions as primary and backup are not permanent and they will change their roles after a roll back or Junos upgrade.

Use the following command to find out which partition is primary and which is backup:

Now, inorder to take a backup of the current root into the other /altroot root (on the same media) use the “request system snapshot slice alternate” command as follows:

Hence the command request system snapshot slice alternate is used to copy the contents of primary partition onto secondary backup partition on the same media. It is worth mentioning that request system snapshot media USB is used to make similar copy of one media onto another media, which is USB. In the above example we discussed dual root, issuing the command “request system snapshot media USB” will duplicate the entire internal media (both root partitions, configurations and everything else) onto the external USB drive.

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