Customizing the Liberty environment

You can customize the Liberty environment by using certain specific variables to support the placement of product binary files and shared resources in read-only file systems.

• Specify environment variables by using server.env files.
  You can use server.env files at the installation and server levels to specify environment variables such as JAVA_HOME, WLP_USER_DIR, and WLP_OUTPUT_DIR. For example:

  # Use a specific Java binary
  JAVA_HOME=/opt/ibm/java-i386-60/jre
  # JAVA_HOME=c:\Java

  Note:

  • The server.env files support only key=value pairs.
  • Empty lines and lines that start with the number sign (#) are ignored.
  • All characters are literal except for the caret (^) in Windows when the caret is used to escape a variable expansion character like the exclamation point (!).
  • There should be no blank space surrounding the equal sign (=).
  • Shell and variable expansion are not supported on Linux systems in version 21.0.0.12 and earlier. For information about using expansion variables on Windows or on Linux in version 22.0.0.1 and later, see Expansion variables on the Open Liberty website.
  • WLP_USER_DIR can be specified only in the ${wlp.install.dir}/etc/server.env file because the purpose of this variable is to specify where the remaining configuration is located. After the remaining configuration is found and merged, no further configuration in a different location is expected, or supported.

  The server management script searches for server.env files in two locations: ${wlp.install.dir}/etc/server.env and ${server.config.dir}/server.env. If both files are present, the contents of the two files are merged; values in the server-level file take precedence over values in the runtime-level file.

  You can also specify these environment variables in the shell environment, but the server.env files take precedence over those variables.

• Customize JVM options by using jvm.options files.
  You can use jvm.options files at the runtime and server levels to specify more server startup options, for example, -X arguments. The options are applied when the start, run, and debug actions are started through the server management script. Be sure to specify only one option per line. For example:

  # Set the maximum heap size to 1024m.
  -Xmx1024m
  
  # Set a system property.
  -Dcom.ibm.example.system.property=ExampleValue
  
  # Enable verbose output for class loading.
  -verbose:class
  
  # Enable verbose garbage collection.
  -verbose:gc
  
  # Specify an alternate verbose garbage collection log on IBM Java Virtual Machines only.
  -Xverbosegclog:verbosegc.log
  
  # Specify additional verbose garbage collection options on HotSpot Java Virtual Machines only.
  -Xloggc:verbosegc.log
  -XX:+PrintGCDetails
  -XX:+PrintGCTimeStamps
  -XX:+PrintHeapAtGC

  You can create multiple jvm.options files in the following locations:

  • ${wlp.install.dir}/usr/shared/jvm.options
  • ${server.config.dir}/configDropins/defaults/jvm.options
  • ${server.config.dir}/jvm.options
  • ${server.config.dir}/configDropins/overrides/jvm.options

  These files are merged in order from the beginning to the end of this list before server start and are used as the JVM options for the server. If none of these files are present, then ${wlp.install.dir}/etc/jvm.options is read.

  Note:

  • Do not put property values in quotation marks.
  • Empty lines and lines that start with the number sign (#) are ignored.
  • All characters are literal except for the caret (^) in Windows when the caret is used to escape a variable expansion character like the exclamation point (!).
  • There should be no blank space surrounding the equal sign (=).
  • Shell and variable expansion are not supported on Linux systems in version 21.0.0.12 and earlier. For information about using expansion variables on Windows or on Linux in version 22.0.0.1 and later, see Expansion variables on the Open Liberty website.