This article explains How to upgrade chassis cluster using simultaneous reboot method

1. The SRX device is in a cluster.
2. Both nodes in the chassis cluster need to have their Junos OS upgraded, and both devices need to be running the same version of the Junos OS.

Here are the steps for upgrading chassis cluster using simultaneous reboot method.

1. Download required Software from support site and upload it to both nodes. The software should be stored in /var/tmp directory.
2. Deactivate preempt for redundancy groups.
3. Deactivate interface and ip-monitoring for redundancy-groups.
4. Install software with the commands below on both the nodes.  For detailed instructions, refer to  Installing the Software .
   

   
   From the local file in /var/tmp

   user@srx>  request system software add no-copy /var/tmp/<Junos-image-name.tgz> no-validate

Note:- Need to use "no-validate" option when upgrading Junos software from pre-Junos 21.2R1 to Junos version 21.2R1 or later

    Unlink - (optional) on J Series Services Routers and SRX devices, this option ensures that the software package is removed at the earliest opportunity in order to make room for the installation to be completed.

   
    Do not reboot until you have executed the above command on each cluster member.
   
   
5. Simultaneously ,  enter the below command on each node:
   
   user@srx>  request system reboot
   
   You can also try to use "request system reboot at hh:mm" to reboot both the nodes at the same time. hh:mm is the time on that device which you can get it from "show system uptime"
   
   
6. After the reboot of both the nodes, wait until the cluster become stable.
7. After the cluster reaches stability, enable preemption for redundancy groups and turn on interface and IP monitoring for redundancy groups which were initially deactivated.

Note: On SRX1600, SRX2300, SRX4100, SRX4120, SRX4300, SRX4700, and SRX5000 with RE3 and later does not support "request system software" command. It supports "request vmhost" command.

For example, "request vmhost software add /var/tmp/junos-vmhost-install-srx-x86-64-X.X.X.tgz no-validate reboot".

Related documents:-

SRX Getting Started - Junos Software Installation/Upgrade
[SRX] How to upgrade Junos OS on a Chassis Cluster
[Junos] Understanding Junos software components and installation package names

Platform-Specific Behavior (SRX1600, SRX2300, SRX4120, SRX4700, and SRX5000 with RE3 and later)