This article provides information on how to check which partition, in a dual boot partition, is the primary and which one is the backup.

There could be dual parition as well as single partitions in the SRX series devuces. You can have the same or a different Junos version on each partition. By executing the show system storage partition command, you can identify which partition is the primary and which one is the backup partition, and also from which partition the device has booted. The following output s a sample taken from a SRX device, which has partition:

show system storage partitions (SRX Series, Dual Root Partitioning)

show system storage partitions

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Boot Media: internal (da0)
Active Partition: da0s2a
Backup Partition: da0s1a
Currently booted from: active (da0s2a)

Partitions Information:
  Partition  Size   Mountpoint
      s1a    293M   altroot
      s2a    293M   /
      s3e    24M    /config
      s3f    342M   /var
      s4a    30M    recovery

As per the above output, da0s2a is the primary partition, da0s1a  is the backup partition, and the device has booted from the primary partition.

show system storage partitions (SRX Series, Single Root Partitioning)

show system storage partitions

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Boot Media: internal (da0)
Partitions Information:
  Partition  Size   Mountpoint
      s1a    898M   /
      s1e    24M    /config
      s1f    61M    /var

2020-09-30: Updated sample outputs.