which command will display all the environment variables on the system
Environment variable In all Unix and Unix-like systems, each process has its own separate set of environment variables. By default, when a process is created, it inherits a duplicate environment of its parent process, except for explicit changes made by the parent when it creates the child. At the API level, these changes must be done between running fork and exec. Alternatively, from command shells such as bash, a user can change environment variables for a particular command invocation by indirectly invoking it via env or using the ENVIRONMENT_VARIABLE=VALUE <command> notation. A running program can access the values of environment variables for configuration purposes.
Single user mode Unix-like operating systems provide single user mode functionality either through the System V-style runlevels, BSD-style boot-loader options, or other boot-time options.
.properties Each parameter is stored as a pair of strings, one storing the name of the parameter (called the key), and the other storing the value.
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