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:
* soft nofile 65536
* hard nofile 131072
* soft nproc 2048
* hard nproc 4096
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：
* soft nproc 1024
#修改为
* soft nproc 2048
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。
问题四：可以访问127.0.0.1:9200，但不能访问 公网IP:9200 后面ip就是127.0.0.1的局域网ip，如何解决？
解决：修改elasticsearch目录下config/elasticsearch.yml，注意要在network下面:
network.host: 0.0.0.0
问题五：启动异常：ERROR: bootstrap checks failed system call filters failed to install; check the logs and fix your configuration or disable system call filters at your own risk
问题原因：因为Centos6不支持SecComp，而ES5.2.1默认bootstrap.system_call_filter为true进行检测，所以导致检测失败，失败后直接导致ES不能启动。详见 ：https://github.com/elastic/elasticsearch/issues/22899
解决：在elasticsearch.yml中配置bootstrap.system_call_filter为false，注意要在Memory下面: bootstrap.memory_lock: false bootstrap.system_call_filter: false
