There are a number of options depending on what client OS and what NBU version.
For Windows, and any NBU version, run the standard windows installer from a cenral server and choose client installation - at one point you can choose to perform a remote installation and if you progress you are given the option to add in multiple servers (you will need to provide remote admin credentials for the install). This will work for upgrades and new installs.
For Unix/Linux etc. and NBU version 8.1.2 or better - you can use VXupdate to run a push install from one of your existing NBU servers (the caveat is that the client must already be running NBU already). this will not work for new installs to any *nix platform. See this link https://www.veritas.com/content/support/en_US/doc/125240132-131571482-0/v131571516-131571482
Veritas also provides Chef and SCCM templates to enable the use of these tools to deploy netbackup. See this link https://sort.veritas.com/utility/netbackup/deployment
Please find the below deatils.
NBU version: 8.1.1
Master server OS: Windos 2008 R2
Client OS: 2008 R2
1. if upgradation how can we do the push installtion?
For NBU 8.1.1, remote install of Windows Clients from Windows master can be found in the NBU 8.1.1 Installation Guide.
See this online version version of the Installation Guide:
Until you upgrade to version 8.1.2 (or later) where vxupdate can be used, the way to upgrade existing clients will be same as new installation