问题出现环境，OS版本：CentOS-6
ES版本：elasticsearch-7.2
1、max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
每个进程最大同时打开文件数太小，可通过下面2个命令查看当前数量
ulimit -Hn
ulimit -Sn
修改/etc/security/limits.conf文件，增加配置，用户退出后重新登录生效
- soft nofile 65536
- hard nofile 65536
2、max number of threads [3818] for user [es] is too low, increase to at least [4096]
问题同上，最大线程个数太低。修改配置文件/etc/security/limits.conf（和问题1是一个文件），增加配置
- soft nproc 4096
- hard nproc 4096
修改文件 /etc/security/limits.d
- soft nproc 1024
修改为 - soft nproc 4096
可通过命令查看
ulimit -Hu
ulimit -Su
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
