Install third party software in ssg 11 appliance encounter error: Package <software> is not available, but is referred to by another package.

Products

• CA API Gateway

Issue/Introduction

Error while installing git

=======================================

Package git is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'git' has no installation candidate

Environment

ssg 11.x

Cause

/etc/apt/sources.list file is empty. 

Resolution

Edit  /etc/apt/sources.list

Add lines: 
deb [trusted=yes] https://deb.debian.org/debian/ bookworm main contrib non-free non-free-firmware
deb [trusted=yes] https://deb.debian.org/debian/ bookworm-updates main contrib non-free non-free-firmware
deb [trusted=yes] https://security.debian.org/debian-security/ bookworm-security main contrib non-free non-free-firmware

Save the file.  

apt update 

apt install git

(apt install <package name> for other software)