安裝ElasticSearch7.6使用自帶JDK

平時使用jdk8，es7啓動會報錯。
需要修改elasticsearch-env配置文件，使用自帶jdk。

future versions of Elasticsearch will require Java 11; your Java version from [d:\Program Files\java\jdk1.8.0_91\jre] does not meet this requirement

linux

 39 if [ ! -z "$JAVA_HOME" ]; then
 40   JAVA="$JAVA_HOME/bin/java"
 41   JAVA_TYPE="JAVA_HOME"
 42 else
 43   if [ "$(uname -s)" = "Darwin" ]; then
 44     # macOS has a different structure
 45     JAVA="$ES_HOME/jdk.app/Contents/Home/bin/java"
 46   else
 47     JAVA="$ES_HOME/jdk/bin/java"
 48   fi
 49   JAVA_TYPE="bundled jdk"
 50 fi

修改成

  if [ "$(uname -s)" = "Darwin" ]; then
    # macOS has a different structure
    JAVA="$ES_HOME/jdk.app/Contents/Home/bin/java"
  else
    JAVA="$ES_HOME/jdk/bin/java"
  fi
  JAVA_TYPE="bundled jdk"

windows
打開 elasticsearch-env.bat文件：

if defined JAVA_HOME (
  set JAVA="%JAVA_HOME%\bin\java.exe"
) else (
  set JAVA="%ES_HOME%\jdk\bin\java.exe"
  set JAVA_HOME="%ES_HOME%\jdk"
)

修改成

set JAVA="%ES_HOME%\jdk\bin\java.exe" 
set JAVA_HOME="%ES_HOME%\jdk" 

然後就可以啓動了。最後又出現如下問題

OpenJDK 64-Bit Server VM warning: Option UseConcMarkSweepGC was deprecated in version 9.0 and will likely be removed in a future release.

打開jvm.options
修改 （大概在35行）

8-13:-XX:+UseConcMarkSweepGC
8-13:-XX:CMSInitiatingOccupancyFraction=75
8-13:-XX:+UseCMSInitiatingOccupancyOnly

改成

8-13:-XX:+UseG1GC
8-13:-XX:CMSInitiatingOccupancyFraction=75
8-13:-XX:+UseCMSInitiatingOccupancyOnly

最後可以啓動了。