問題出現的環境：
OS版本：CentOS-7-x86_64-Minimal-1708
ES版本：elasticsearch-6.2.2
1. max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
每個進程最大同時打開文件數太小，可通過下面2個命令查看當前數量
ulimit -Hn ulimit -Sn
修改/etc/security/limits.conf文件，增加配置，用戶退出後重新登錄生效
* soft nofile 65536 * hard nofile 65536
2. max number of threads [3818] for user [es] is too low, increase to at least [4096]
問題同上，最大線程個數太低。修改配置文件/etc/security/limits.conf，增加配置
可通過命令查看
ulimit -Hu ulimit -Su
按照如下更改：
* soft nproc 4096 * hard nproc 4096
3. max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
修改/etc/sysctl.conf文件，增加配置vm.max_map_count=262144
vi /etc/sysctl.conf sysctl -p
執行命令sysctl -p生效
4. Exception in thread "main" java.nio.file.AccessDeniedException: /usr/local/elasticsearch/elasticsearch-6.2.2-1/config/jvm.options
elasticsearch用戶沒有該文件夾的權限，執行命令
chown -R es:es /usr/local/elasticsearch/