-sh-4.2$ ls -al
drwxr-xr-x 2 hrawat abp         0 Mar 30 08:06 .
drwxr-xr-x 6 hrawat abp         0 Mar 30 08:06 ..
-rw-r--r-- 1 hrawat abp 159081279 Jan 26 11:37 RocketAPIGWUnixLinux.run

-sh-4.2$ chmod 744 RocketAPIGWUnixLinux.run
-sh-4.2$ ls -al
drwxr-xr-x 2 hrawat abp         0 Mar 30 08:06 .
drwxr-xr-x 6 hrawat abp         0 Mar 30 08:06 ..
-rwxr--r-- 1 hrawat abp 159081279 Jan 26 11:37 RocketAPIGWUnixLinux.run
​

4) Run the install file:

-sh-4.2$ ./RocketAPIGWUnixLinux.run

Verifying archive integrity...  100%   All good.
Uncompressing Rocket API Gateway Setup  100%
=============================================================================
                       Rocket Software Installation
=============================================================================
Welcome to the Rocket API Gateway Setup

This wizard will guide you through the installation of Rocket API Gateway


Specify an instance name
Leave empty for default value or input Q for quit
Default: Default

Instance name: APIGW01

Specify destination directory
Leave empty for default value or input Q for quit
Default: /opt/rocketsoftware/rocketapigateway/APIGW01

Destination directory:

Specify HTTP Admin port
Leave empty for default value or input Q for quit
Default: 8180

HTTP Admin Port:

Use the Access and Connectivity Hub (Y=Yes, N=No, Q=Abort)? N

Installation in progress, please wait...

You have successfully installed Rocket API Gateway

  The following parameters were used:
  Destination directory: /opt/rocketsoftware/rocketapigateway/APIGW01
  Instance name: APIGW01
  HTTP Admin port: 8180
  Hub address:
  Hub realm:
  Hub environment:
  Hub engine UUID:

Thank you for installing Rocket Software

5) In the above output we see that the API GW has been installed with an instance name of APIGW01, in directory /opt/rocketsoftware/rocketapigateway/APIGW01 and using port 8180. This setup does not use the Rocket API HUB.

6) Start API GW:

-sh-4.2$ cd /opt/rocketsoftware/rocketapigateway/APIGW01

-sh-4.2$ ls
bin  config  hub.cfg  lib  MSMQConnectionInterface.dll  NOTICES  resources  start-server-mq.sh  start-server.sh  stop-server.sh

-sh-4.2$ ./start-server.sh
SERVER_NAME:APIGW01
CONFIG_DIR:config
JDK Version 8 detected, endorsed support
Starting in the background
-sh-4.2$ nohup: appending output to 'nohup.out'

7) You can check the GW status using following command:

-sh-4.2$ pwd
/opt/rocketsoftware/rocketapigateway/APIGW01

-sh-4.2$ tail -2 log/gateway-20210330081753.log
2021-03-30 08:17:54,785 INFO  [main][com.seagullsw.appinterface.server.AppInterfaceServer] RUNNING AppInterfaceServer
2021-03-30 08:17:54,785 INFO  [main][com.seagullsw.appinterface.server.AppInterfaceServer.StartUp.Complete] Rocket API Gateway start-up completed, Version 8.5.5 (build 8.3875.0.0/648).

8) To check the running process use the following:

-sh-4.2$ ps -aux | grep -i APIGW01 | grep -v grep
hrawat    61406  0.2  3.1 4605264 255220 pts/0  Sl   08:41   0:06 java -Xbootclasspath/a:/lib/tools.jar -Dcom.seagullsw.server.name=APIGW01 -Djava.endorsed.dirs=lib/endorsed -Djavax.xml.transform.TransformerFactory=org.apache.xalan.xsltc.trax.SmartTransformerFactoryImpl -Dorg.apache.cxf.Logger=org.apache.cxf.common.logging.Log4jLogger -Dcom.seagullsw.lde.config.dir=config com.seagullsw.appinterface.server.AppInterfaceServer --strictStart -c config
-sh-4.2$

9) Make sure to generate a license file (.SAF) and place it at installation directory. 

Hope this is helpful! Let me know if you run into any troubles or need instructions for other platforms or environments.