How to pass the -D additional parameter while starting tomcat?

I have tested params for Tomcat 7/8 on Windows 10 and CentOs 7 (Linux).
1) On Windows need to create setenv.bat in the {TOMCAT_HOME}/bin/ path and insert there such code:

set CATALINA_OPTS=-Dapp.username=admin -Dapp.password=12345

IMPORTANT: do not use quotes (" ") for setting params on windows.

2) On CentOs need to create setenv.sh in the {TOMCAT_HOME}/bin/ path and insert there such code:

export CATALINA_OPTS="-Dapp.username=admin -Dapp.password=12345"

You can also create {TOMCAT_HOME}/conf/conf.d/custom.conf and insert the same export command there.

You can set an environment variable to do that. E.g. in Linux:

export JAVA_OPTS="-Dapp.username -Dapp.username"

Or in Windows:

set JAVA_OPTS="-Dapp.username -Dapp.username"

Do this before starting Tomcat

You will want to set the CATALINA_OPTS system variable - this is read by Tomcat (and only by Tomcat) when starting. As @Betoverse says you can set this using the two methods:

export CATALINA_OPTS="-Dapp.username -Dapp.username"

Or in Windows:

set CATALINA_OPTS="-Dapp.username -Dapp.username"

You can add that command to your ~/.profile on UNIX to have it set automatically.

For Tomcat 6 you should add the params to the startup.sh (Windows startup.bat). For Tomcat 7 and above you should set the parameters in the {Catalina Root}/bin/setenv.sh like such:

export CATALINA_OPTS="$CATALINA_OPTS -Dapp.username=username -Dapp.password=password"

Or in Windows:

set CATALINA_OPTS="$CATALINA_OPTS -Dapp.username=username -Dapp.password=password"

NOTE: Notice the $CATALINA_OPTS at the beginning so you don't wipe out any previously set values. Not doing so can create a very hard to debug problem!

If the parameters you are setting are solely to be used by Tomcat then be sure to set it using CATALINA_OPTS.

If your application will be using the parameters then be sure to use JAVA_OPTS instead. Tomcat will also read these parameters. This can also go in the setenv.sh file. For instance:

export JAVA_OPTS="$JAVA_OPTS -Dapp.username=username -Dapp.password=password"

Or in Windows:

set JAVA_OPTS="$JAVA_OPTS -Dapp.username=username -Dapp.password=password"