1、ES启动报错：不能使用root用户
[root@weshare bin]# ./elasticsearch
[2019-10-02T19:40:42,296][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-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:112) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:124) ~[elasticsearch-cli-6.1.1.jar:6.1.1]
at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:85) ~[elasticsearch-6.1.1.jar:6.1.1]
Caused by: java.lang.RuntimeException: can not run elasticsearch as root
at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:104) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:171) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:322) ~[elasticsearch-6.1.1.jar:6.1.1]
at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:121) ~[elasticsearch-6.1.1.jar:6.1.1]
... 6 more
解决方法：新建其他用户，并把ES安装目录赋给该用户，切换该用户，启动ES
详细过程：创建一个用户来专门启动 ES
groupadd esgroup 创建ES用户组
useradd es-admin 创建ES用户
passwd es-admin 给用户赋密码
abc123456 密码
chown -R esgroup:es-admin elasticsearch-7.2.0 更改ES安装文件夹及内部文件的所属用户为es-admin ，elasticsearch-7.2.0为你ES的安装目录名称
su es-admin 切换到es-admin用户再启动
cd elasticsearch-7.2.0/bin 进入你的ES目录下的bin目录
./elasticsearch 启动ES
2、ES启动报错：jdk的安全策略问题
[2019-07-25T18:17:30,305][INFO ][o.e.b.BootstrapChecks ] [node-1] bound or publishing to a non-loopback address, enforcing bootstrap checks
ERROR: [1] bootstrap checks failed
[1]: granting the all permission effectively disables security
解决方法：把jre中的java.policy删掉，启动成功
3、ES启动报错：系统能打开的最大文件数量太小
max file descriptors [65535] for elasticsearch process is too low, increase to at least [65536]
解决方法：修改文件改动默认配置，命令：sudo vim /etc/security/limits.conf
修改为：
root soft nofile 65536
root hard nofile 65536
user1 soft nofile 65536 #user1为普通用户，可以改为 ，即所有普通用户
user1 hard nofile 65536 #user1为普通用户，可以改为，即所有普通用户
(注意，重启之后配置才能生效)
4、ES启动报错：使用虚拟内存过小
max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
解决方法：修改文件改动默认配置，命令：sudo vim /etc/sysctl.conf
增加这一行：vm.max_map_count=655360
刷新配置：sysctl -p
(注意，重启之后配置才能生效)
5、ES启动报错：内存不足
解决方法：vi jvm.options （jvm.options在ES安装目录的config里面）
es 5.x版本默认启动内存需要4g ，对于一些低内存的虚拟机或者云服务器可能无法启动，需要修改默认内存参数
默认是：
-Xms4g
-Xmx4g
可以修改为：
-Xms1g
-Xmx1g
6、ES启动报错：外网不能访问
Caused by: java.net.BindException: Cannot assign requested address
解决方法：配置外网
cd elasticsearch-7.2.0/config
vi elasticsearch.yml
将 network.host: 192.168.0.1 修改为本机IP 0.0.0.0
7、ES启动报错：没有执行权限
./elasticsearch: Permission denied
解决方法：
授权执行命令 chmod +x bin/elasticsearch
-----------------------------看到以下标识这段话启动正常了---------------------------
license [44e05c9c-2cb2-4e07-9cc4-627142e154b1] mode [basic] - valid
此时在服务器上执行： curl ip:port
如：curl 127.0.0.1:9200
{
"name" : "weshare002",
"cluster_name" : "elasticsearch",
"cluster_uuid" : "5wRNqjWBR0ia6qzExFr7-A",
"version" : {
"number" : "7.2.0",
"build_flavor" : "default",
"build_type" : "tar",
"build_hash" : "508c38a",
"build_date" : "2019-06-20T15:54:18.811730Z",
"build_snapshot" : false,
"lucene_version" : "8.0.0",
"minimum_wire_compatibility_version" : "6.8.0",
"minimum_index_compatibility_version" : "6.0.0-beta1"
},
"tagline" : "You Know, for Search"
}
