1.org.elasticsearch.bootstrap.StartupException: java.lang.RuntimeException: can not run elasticsearch as root
不能用root身份登录
解决办法
groupadd student useradd mm -g student -p 123
chown -R pp:student elasticsearch-7.0.0
切换至pp用户登录运行，成功
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2.Cannot allocate memory'
无法分配内存
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3. max file descriptors [4096] for elasticsearch process is too low, increase to at least [65535]
对于elasticsearch进程，max文件描述符[4096]过低，至少增加到[65535]
vi /etc/security/limits.conf
添加如下内容:
* soft nofile 65536
* hard nofile 65536
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4.max number of threads [3758] for user [pp] is too low, increase to at least [4096]
用户最多线程数[3758][pp]太低，至少增加到[4096]
* soft nproc 4096
* hard nproc 4096
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5.max virtual memory areas vm.max_map_count [65530] is too low, increase to at least [262144]
最大虚拟内存区域vm。max_map_count[65530]太低，至少增加到[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
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6.the default discovery settings are unsuitable for production use; at least one of [discovery.seed_hosts, discovery.seed_providers, cluster.initial_master_nodes] must be configured
默认的发现设置不适合生产使用;至少有一个[发现]。seed_hosts,发现。seed_providers,集群。必须配置initial_master_nodes]