CentOS 7.9 安装 Elasticsearch 7.8.1
安装环境
CentOS 安装的是最小版本：CentOS-7-x86_64-Minimal-2009
1[root@localhost ~]# cat /etc/redhat-release
2CentOS Linux release 7.9.2009 (Core)
关闭防火墙：
1systemctl stop firewalld.service
2systemctl disable firewalld.service
前期准备
新建用户
默认情况下，Elasticsearch 不允许使用 root 用户启动。
1groupadd esgroup
2useradd esapp -g esgroup
修改资源配置
修改 /etc/security/limits.conf 文件，在文件中添加以下内容：
1esapp - nofile 65535
2esapp - nproc 4096
修改 /etc/sysctl.conf 文件，在文件中添加以下内容：
1vm.max_map_count=262144
禁用内存交换
临时关闭命令：
1swapoff -a
永久修改的方法：修改 /etc/fstab 文件，将注释掉所有包含 swap 的行。
全部配置完后，重启电脑，因为有些配置需要重启电脑才能生效。
关于 Java
因为 Elasticsearch 自带了 OpenJDK，所以我这里没有额外安装 JDK。
下载安装
使用 esapp 用户登录，或使用 su - esapp 切换到 esapp 用户，运行下面的命令：
1wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.8.1-linux-x86_64.tar.gz
2wget https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-7.8.1-linux-x86_64.tar.gz.sha512
3shasum -a 512 -c elasticsearch-7.8.1-linux-x86_64.tar.gz.sha512
4tar -xzf elasticsearch-7.8.1-linux-x86_64.tar.gz
5cd elasticsearch-7.8.1/
如果在校验时，提示 -bash: shasum: command not found，则需要安装 perl-Digest-SHA
1yum install -y perl-Digest-SHA
修改配置文件
1cd /home/esapp/elasticsearch-7.8.1/config
2cp elasticsearch.yml elasticsearch.yml.bak
3vi elasticsearch.yml
将 network.host: 192.168.0.1 改为 network.host: 0.0.0.0 并取消注释。以便外部浏览器可以访问。
添加 discovery.type: single-node。
启动并验证
启动
1# 依然使用普通用户
2cd /home/esapp/elasticsearch-7.8.1/bin
3# 启动
4./elasticsearch
检查是否启动成功
打开新的终端，输入下面的命令。
1[root@localhost ~]# curl -X GET "localhost:9200/?pretty"
2{
3 "name" : "localhost.localdomain",
4 "cluster_name" : "elasticsearch",
5 "cluster_uuid" : "7iE1xknOQLiIJiDnK7dJug",
6 "version" : {
7 "number" : "7.8.1",
8 "build_flavor" : "default",
9 "build_type" : "tar",
10 "build_hash" : "b5ca9c58fb664ca8bf9e4057fc229b3396bf3a89",
11 "build_date" : "2020-07-21T16:40:44.668009Z",
12 "build_snapshot" : false,
13 "lucene_version" : "8.5.1",
14 "minimum_wire_compatibility_version" : "6.8.0",
15 "minimum_index_compatibility_version" : "6.0.0-beta1"
16 },
17 "tagline" : "You Know, for Search"
18}
在非本地浏览器中访问 http://ES所在机器的IP:9200/，正常的话同样也可以得到上面的信息。
若尝试使用 root 用户启动，则会报错：
1[root@localhost bin]# ./elasticsearch
2[2021-12-31T02:26:51,276][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [localhost.localdomain] uncaught exception in thread [main]
3org.elasticsearch.bootstrap.StartupException: java.lang.RuntimeException: can not run elasticsearch as root
4 at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:174) ~[elasticsearch-7.8.1.jar:7.8.1]
5 at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:161) ~[elasticsearch-7.8.1.jar:7.8.1]
6 at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-7.8.1.jar:7.8.1]
7 at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:127) ~[elasticsearch-cli-7.8.1.jar:7.8.1]
8 at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-7.8.1.jar:7.8.1]
9 at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:126) ~[elasticsearch-7.8.1.jar:7.8.1]
10 at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92) ~[elasticsearch-7.8.1.jar:7.8.1]
11Caused by: java.lang.RuntimeException: can not run elasticsearch as root
12 at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:111) ~[elasticsearch-7.8.1.jar:7.8.1]
13 at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:178) ~[elasticsearch-7.8.1.jar:7.8.1]
14 at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:393) ~[elasticsearch-7.8.1.jar:7.8.1]
15 at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:170) ~[elasticsearch-7.8.1.jar:7.8.1]
16 ... 6 more
17uncaught exception in thread [main]
18java.lang.RuntimeException: can not run elasticsearch as root
19 at org.elasticsearch.bootstrap.Bootstrap.initializeNatives(Bootstrap.java:111)
20 at org.elasticsearch.bootstrap.Bootstrap.setup(Bootstrap.java:178)
21 at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:393)
22 at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:170)
23 at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:161)
24 at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86)
25 at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:127)
26 at org.elasticsearch.cli.Command.main(Command.java:90)
27 at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:126)
28 at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92)
29For complete error details, refer to the log at /home/esapp/elasticsearch-7.8.1/logs/elasticsearch.log