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[SRX] Repartition/Reimaging on Junos to address Disk Failure



Article ID: KB35814 KB Last Updated: 22 May 2020Version: 1.0

This article explains the need to partition the internal media and situations in which one can choose to re-partition on SRX series devices.

In earlier Junos versions, both the primary and backup Junos OS images were located on the same root partition. So when there is corruption in the root file system, the entire system fails to boot. 

When no partitioning has been performed on the internal media, the storage partition looks like this:

user@router> show system storage partitions
Boot Media: internal (da0)
Partitions Information:
  Partition  Size   Mountpoint
      s1a    898M   /
      s1e    24M    /config
      s1f    61M    /var

In the case of dual root partitioning, primary and backup Junos OS can be maintained in two independently bootable root partitions. 

In situations when there is a transient disk failure, one can choose to re-image/re-partition the RE. While in most cases, this should rectify the disk issue. If it does not, there could be permanent damage on the disk and might need an RE reboot followed by RE replacement.

Sample Error Message:

Apr 13 03:40:39.723 2019 chassisd[3688]: CHASSISD_SNMP_TRAP7: SNMP trap generated: Hard Disk Failed (jnxFruContentsIndex 9, jnxFruL1Index 1, jnxFruL2Index 0, jnxFruL3Index 0, jnxFruName node0 Routing Engine, jnxFruType 6, jnxFruSlot 0)

Re-partitioning means re-imaging the device with the same software version while creating dual root partitions. It enables the customer to format the internal media and installs the new Junos OS image on the media with dual-root partitioning. The dual-root partitions help SRX Series devices to remain functional even if the file system is corrupted. Also, it helps to facilitate easy recovery of the file system. 

If the primary root partition becomes corrupted, the system can still boot from the backup Junos OS image located in the other root partition maintaining high availability of the system. The boot order is always first primary followed by the backup partition from the internal boot media.

By default, the SRX devices are factory formatted with dual partitions. Dual partitioning is available starting with Junos 10.0 release.

In case of disk failures, re-partitioning will enable initiating the partition process all over again and reboots the device with the newly formed partitions.

Use the following command to perform re-partitioning:

"request system software add <package-name> no-validate partition"
user@router> request system software add /var/tmp/junos-srxmr-17.3R2.10.domestic.tgz no-validate partition
Checking for free space on /var/tmp/install
Copying package /var/tmp/junos-srxmr-17.3R2.10.domestic.tgz to /var/tmp/install
Checking for basic sanity of copied package
WARNING: Installation with partition option will take several minutes to complete
WARNING: Please do not power-cycle the system till the installation is over
WARNING: A reboot is required to install the software
WARNING: Use the 'request system reboot' command immediately
user@router> request system reboot

NOTE: If you do not add 'no-validate'  to the above command, it might return a validation error. It is recommended to use 'no-validate'.

After RE reboots, verify the partitions:

user@router> show system storage partitions
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

user@router> show system snapshot media internal
Information for snapshot on       internal (/dev/da0s1a) (primary)
Creation date: May 18 02:31:19 2020
JUNOS version on snapshot:
  junos  : 17.3R2.10-domestic
Information for snapshot on       internal (/dev/da0s2a) (backup)
Creation date: May 18 02:29:41 2020
JUNOS version on snapshot:
  junos  : 17.3R2.10-domestic

​By achieving the above, we can ensure that if the system fails to boot up from primary partition due to some unexpected corruption, we still have the secondary partition with an OS snapshot created in it, that can help us boot up your device.

IMPORTANT: Please note that this method will erase & re-partition the whole internal media, but it should preserve the current configuration. Be sure to perform a data/configuration backup before starting.

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