How to fix Elasticsearch crashing upon startup?

If Elasticsearch crashes after starting up, it could be due to a few reasons and can be resolved as follows:

1. Insufficient memory: Elasticsearch requires a larger amount of memory to run properly. You can increase the memory limit by modifying the jvm.options file. Open the jvm.options file and locate the -Xms and -Xmx parameters, increase their values to raise the memory limit. For example, increase both -Xms and -Xmx values to 4GB: -Xms4g and -Xmx4g.
2. Insufficient hardware resources: Elasticsearch operates best with adequate hardware resources. Ensure that the server has enough CPU and memory, and sufficient disk space.
3. Port conflict: Elasticsearch by default uses ports 9200 and 9300. Make sure these ports are not being used by any other programs. You can check the port usage by running the command “netstat -ano” and find the process ID occupying the port.
4. Error in the log file: Check the Elasticsearch log file, typically located in the logs directory. The log file may contain detailed information about the crash causes for better troubleshooting.
5. Java version conflict: Elasticsearch requires Java 8 or higher to run. Make sure you have the correct Java version installed and that the JAVA_HOME environment variable is correctly set.

If the above methods do not solve the issue, you can try reinstalling Elasticsearch, making sure to configure it correctly and install any necessary dependencies.