Unable to upgrade SRX cluster using ISSU/ICU from Junos Space.

SRX cluster is not getting upgraded using ISSU/ICU from Junos Space on version 16.1. The upgrade fails with following error:

Node0: Unexpected sysctl return
error: unknown command: /sbin/sysctl

At the same, unable to perform ISSU/ICU upgrade directly from SRX CLI with the following command:

root@SRXNode0> request  system    software  in-service-upgrade    no-validate    /var/tmp/junos-srxsme-12.3X48-D40.5-domestic.tgz    no-sync

In Junos Space DEBUG log, the following RPC was triggered in server.log:

<rpc message-id="1"> <request-package-in-service-upgrade> <no-validate/> <package-name> /var/tmp/junos-srxsme-12.3X48-D40.5-domestic.tgz <no-sync/>

The error, 'error: unknown command: /sbin/sysctl' is a response from SRX in ISSU/ICU upgrade RPC due to a user privilege issue.

Use only ' root ' user for ISSU/ICU upgrade from Junos Space. Even the 'Super Class' user will not work.

Notes:

• ISSU/ICU works for FXP managed SRX Clusters when both devices are individually discovered in Junos Space. [User: root]
• ISSU/ICU works for SRX Clusters being managed via "master-only" IP in Junos Space. [User: root]
• reth (SRX VC) based managed clusters in Junos Space is not supported for ISSU/ICU untill version 16.1.