一、什么是elasticSearch

1. 基于Lucene的搜索框架, 它提供了一个分布式多用户能力的全文搜索引擎，基于RESTful web接口
2. 上手容易，拓展节点方便，可用于存储和检索海量数据，接近实时搜索，海量数据量增加，搜索响应性能几乎不受影响；
3. 分布式搜索框架，自动发现节点，副本机制，保障可用性

二、安装elasticSerach

1. wget 下载elasticsearch安装包
   wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.2.2.tar.gz
2. 解压
   tar -zxvf elasticsearch-6.2.2.tar.gz

三、 配置es出现相关问题处理：

    1、问题一
        Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x00000000c5330000, 986513408, 0) failed; error='Cannot allocate memory' (errno=12)
        #
        # There is insufficient memory for the Java Runtime Environment to continue.
        # Native memory allocation (mmap) failed to map 986513408 bytes for committing reserved memory.
        # An error report file with more information is saved as:
        # /usr/local/software/temp/elasticsearch-6.2.2/hs_err_pid1912.log
    解决：内存不够，增加内存
    2、问题二
        [root@iZwz95j86y235aroi85ht0Z bin]# ./elasticsearch
        [2018-02-22T20:14:04,870][WARN ][o.e.b.ElasticsearchUncaughtExceptionHandler] [] uncaught exception in thread [main]
        org.elasticsearch.bootstrap.StartupException: java.lang.RuntimeException: can not run elasticsearch as root
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:125) ~[elasticsearch-6.2.2.jar:6.2.2]
        at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:112) ~[elasticsearch-6.2.2.jar:6.2.2]
        at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.2.2.jar:6.2.2]
        at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.2.2.jar:6.2.2]
    解决：用非root用户
        添加用户：useradd -m 用户名  然后设置密码  passwd 用户名
    3、问题三
        ./elasticsearch
        Exception in thread "main" java.nio.file.AccessDeniedException: /usr/local/software/temp/elasticsearch-6.2.2/config/jvm.options
       解决：权限不够 chmod 777 -R 当前es目录