⑴ 解决ElasticSearch启动报错
新建普通用户启动报错：Error: Could not find or load main class org.elasticsearch.tools.javaVersionChecker Elasticsearch requires at least Java 8 but your Java version from /usr/java/jdk1.8.0_112/bin/java does not meet this requirement
解决方法：将es放到admin目录下运行
运行发现报以下错误：
这是admin权限不够的导致，解决办法，将用户切换到root用户，退出到elasticseach-5.4.0的父目录，执行以下命令：
chown admin elasticsearch-5.4.0 -R
切换到admin用户启动es发现报以下错误：
bootstrap.memory_lock: false
bootstrap.system_call_filter: false
配置集群后启动报以下错误：
问题一：ERROR: bootstrap checks failed
max file descriptors [4096] for elasticsearch process likely too low, increase to at least [65536]
max number of threads [1024] for user [lishang] likely too low, increase to at least [2048]
解决：切换到root用户，编辑limits.conf 添加类似如下内容
vi /etc/security/limits.conf
添加如下内容:
问题二：max number of threads [1024] for user [lish] likely too low, increase to at least [2048]
解决：切换到root用户，进入limits.d目录下修改配置文件。
vi /etc/security/limits.d/90-nproc.conf
修改如下内容：
问题三：max virtual memory areas vm.max_map_count [65530] likely too low, increase to at least [262144]
解决：切换到root用户修改配置sysctl.conf
vi /etc/sysctl.conf
添加下面配置：
vm.max_map_count=655360
并执行命令：
sysctl -p
然后，重新启动elasticsearch，即可启动成功。