问题一
今天下午，在新配置的虚拟机中采用普通用户对elsaticsearch进行安装的时候，在使用命令bin/elasticsearch对其进行启动的时候，出现下述所示的报错信息：
[admin@admin04 elasticsearch-5.2.2]$ bin/elasticsearch
Exception in thread "main" java.lang.UnsupportedClassVersionError: org/elasticsearch/bootstrap/Elasticsearch : Unsupported major.minor version 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:482)
在之前安装部署的过程中，并没有出现此现象。经过多方查询原因得知，可能会是centos自带的open jdk出现的问题。首先需要查看本机是否含有open jdk版本信息，如果有则进行卸载，并安装apache原生的jdk版本。
解决方法：
1.查看本地是否含有 open jdk
[root@admin04 ~]# rpm -qa|grep java
java-1.7.0-openjdk-1.7.0.45-2.4.3.3.el6.x86_64
java-1.6.0-openjdk-1.6.0.0-1.66.1.13.0.el6.x86_64
tzdata-java-2013g-1.el6.noarch
2.卸载查询到的Java包
[root@admin04 ~]# rpm -e --nodeps java-1.7.0-openjdk-1.7.0.45-2.4.3.3.el6.x86_64
[root@admin04 ~]# rpm -e --nodeps java-1.6.0-openjdk-1.6.0.0-1.66.1.13.0.el6.x86_64
[root@admin04 ~]# rpm -e --nodeps tzdata-java-2013g-1.el6.noarch
3.安装apache的原生jdk版本，并配置环境变量
[root@admin04 jdk1.8.0_162]# tar -zxvf jdk-8u162-linux-x64.tar.gz -C /home/admin/opt/softwares/
[root@admin04 jdk1.8.0_162]# vi /etc/profile
[root@admin04 jdk1.8.0_162]# source /etc/profile
[root@admin04 ~]# java -version
java version "1.8.0_162"
Java(TM) SE Runtime Environment (build 1.8.0_162-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.162-b12, mixed mode)
- 验证能否正常启动
[admin@admin04 elasticsearch-5.2.2]$ bin/elasticsearch
[2019-08-27T15:27:19,837][INFO ][o.e.n.Node ] [admin01] initializing ...
[2019-08-27T15:27:20,081][INFO ][o.e.e.NodeEnvironment ] [admin01] using [1] data paths, mounts [[/ (/dev/mapper/vg_admin04-lv_root)]], net usable_space [12.7gb], net total_space [17.2gb], spins? [possibly], types [ext4]
[2019-08-27T15:27:20,083][INFO ][o.e.e.NodeEnvironment ] [admin01] heap size [1.9gb], compressed ordinary object pointers [true]
[2019-08-27T15:27:20,087][INFO ][o.e.n.Node ] [admin01] node name [admin01], node ID [TYpjsmE9Sw2cjLWeklFaXA]
[2019-08-27T15:27:20,093][INFO ][o.e.n.Node ] [admin01] version[5.2.2], pid[3241], build[f9d9b74/2017-02-24T17:26:45.835Z], OS[Linux/2.6.32-431.el6.x86_64/amd64], JVM[Oracle Corporation/Java HotSpot(TM) 64-Bit Server VM/1.8.0_162/25.162-b12]
[2019-08-27T15:27:23,532][INFO ][o.e.p.PluginsService ] [admin01] loaded module [aggs-matrix-stats]
[2019-08-27T15:27:23,533][INFO ][o.e.p.PluginsService ] [admin01] loaded module [ingest-common]
[2019-08-27T15:27:23,533][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-expression]
[2019-08-27T15:27:23,534][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-groovy]
[2019-08-27T15:27:23,534][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-mustache]
[2019-08-27T15:27:23,534][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-painless]
[2019-08-27T15:27:23,535][INFO ][o.e.p.PluginsService ] [admin01] loaded module [percolator]
[2019-08-27T15:27:23,537][INFO ][o.e.p.PluginsService ] [admin01] loaded module [reindex]
[2019-08-27T15:27:23,537][INFO ][o.e.p.PluginsService ] [admin01] loaded module [transport-netty3]
[2019-08-27T15:27:23,537][INFO ][o.e.p.PluginsService ] [admin01] loaded module [transport-netty4]
[2019-08-27T15:27:23,544][INFO ][o.e.p.PluginsService ] [admin01] no plugins loaded
[2019-08-27T15:27:32,907][INFO ][o.e.n.Node ] [admin01] initialized
[2019-08-27T15:27:32,914][INFO ][o.e.n.Node ] [admin01] starting ...
[2019-08-27T15:27:33,958][INFO ][o.e.t.TransportService ] [admin01] publish_address {192.168.47.101:9300}, bound_addresses {192.168.47.101:9300}
[2019-08-27T15:27:33,979][INFO ][o.e.b.BootstrapChecks ] [admin01] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
ERROR: bootstrap checks failed
max file descriptors [4096] for elasticsearch process is too low, increase to at least [65536]
max number of threads [1024] for user [admin] is too low, increase to at least [2048]
[2019-08-27T15:27:34,019][INFO ][o.e.n.Node ] [admin01] stopping ...
[2019-08-27T15:27:34,087][INFO ][o.e.n.Node ] [admin01] stopped
[2019-08-27T15:27:34,087][INFO ][o.e.n.Node ] [admin01] closing ...
[2019-08-27T15:27:34,130][INFO ][o.e.n.Node ] [admin01] closed
问题二
此时，可以看见能够正常启动，但是浏览到最后，发现会自动停止运行程序
[2019-08-27T15:27:34,019][INFO ][o.e.n.Node ] [admin01] stopping ...
[2019-08-27T15:27:34,087][INFO ][o.e.n.Node ] [admin01] stopped
[2019-08-27T15:27:34,087][INFO ][o.e.n.Node ] [admin01] closing ...
[2019-08-27T15:27:34,130][INFO ][o.e.n.Node ] [admin01] closed
如上所示，其实解决这个问题的方法很简单。
在ElasticSearch安装部署中，我们介绍了需要用普通用户启动，同时需要利用root用户修改相应的信息。因此我们会尽可能打开多的操作窗口进行一次性操作，此时当我们在使用sysctl -p在root界面进行操作，然后使用bin/elasticsearch在普通用户下执行自然会报错。
解决方法
当root界面操作完sysctl -p之后，重新打开一个普通用户的操作窗口执行启动会成功。
[admin@admin04 elasticsearch-5.2.2]$ bin/elasticsearch
[2019-08-27T15:50:32,044][INFO ][o.e.n.Node ] [admin01] initializing ...
[2019-08-27T15:50:32,270][INFO ][o.e.e.NodeEnvironment ] [admin01] using [1] data paths, mounts [[/ (/dev/mapper/vg_admin04-lv_root)]], net usable_space [12.7gb], net total_space [17.2gb], spins? [possibly], types [ext4]
[2019-08-27T15:50:32,272][INFO ][o.e.e.NodeEnvironment ] [admin01] heap size [1.9gb], compressed ordinary object pointers [true]
[2019-08-27T15:50:32,276][INFO ][o.e.n.Node ] [admin01] node name [admin01], node ID [TYpjsmE9Sw2cjLWeklFaXA]
[2019-08-27T15:50:32,282][INFO ][o.e.n.Node ] [admin01] version[5.2.2], pid[3494], build[f9d9b74/2017-02-24T17:26:45.835Z], OS[Linux/2.6.32-431.el6.x86_64/amd64], JVM[Oracle Corporation/Java HotSpot(TM) 64-Bit Server VM/1.8.0_162/25.162-b12]
[2019-08-27T15:50:35,701][INFO ][o.e.p.PluginsService ] [admin01] loaded module [aggs-matrix-stats]
[2019-08-27T15:50:35,702][INFO ][o.e.p.PluginsService ] [admin01] loaded module [ingest-common]
[2019-08-27T15:50:35,702][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-expression]
[2019-08-27T15:50:35,702][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-groovy]
[2019-08-27T15:50:35,704][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-mustache]
[2019-08-27T15:50:35,706][INFO ][o.e.p.PluginsService ] [admin01] loaded module [lang-painless]
[2019-08-27T15:50:35,706][INFO ][o.e.p.PluginsService ] [admin01] loaded module [percolator]
[2019-08-27T15:50:35,708][INFO ][o.e.p.PluginsService ] [admin01] loaded module [reindex]
[2019-08-27T15:50:35,712][INFO ][o.e.p.PluginsService ] [admin01] loaded module [transport-netty3]
[2019-08-27T15:50:35,713][INFO ][o.e.p.PluginsService ] [admin01] loaded module [transport-netty4]
[2019-08-27T15:50:35,713][INFO ][o.e.p.PluginsService ] [admin01] no plugins loaded
[2019-08-27T15:50:44,342][INFO ][o.e.n.Node ] [admin01] initialized
[2019-08-27T15:50:44,346][INFO ][o.e.n.Node ] [admin01] starting ...
[2019-08-27T15:50:45,132][INFO ][o.e.t.TransportService ] [admin01] publish_address {192.168.47.101:9300}, bound_addresses {192.168.47.101:9300}
[2019-08-27T15:50:45,155][INFO ][o.e.b.BootstrapChecks ] [admin01] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
[2019-08-27T15:50:48,416][INFO ][o.e.c.s.ClusterService ] [admin01] new_master {admin01}{TYpjsmE9Sw2cjLWeklFaXA}{yFAvxXmeR5-RQchFvRiTyQ}{192.168.47.101}{192.168.47.101:9300}, reason: zen-disco-elected-as-master ([0] nodes joined)
[2019-08-27T15:50:48,542][INFO ][o.e.g.GatewayService ] [admin01] recovered [0] indices into cluster_state
[2019-08-27T15:50:48,639][INFO ][o.e.h.HttpServer ] [admin01] publish_address {192.168.47.101:9200}, bound_addresses {192.168.47.101:9200}
[2019-08-27T15:50:48,640][INFO ][o.e.n.Node ] [admin01] started