这篇文章仅用来记录如何在Linux环境下安装RocketMQ，方便下次要再次安装可以快速找到教程。同时记录了在安装过程中可能出现的问题。本文下载的是4.4.0版本的RocketMQ。需要环境：CentOS6系统，JDK1.8+（配置好$JAVA_HOME），Maven 3.2+。
1、下载安装包，从官网下载对应的压缩包（https://www.apache.org/dyn/closer.cgi?path=rocketmq/4.4.0/rocketmq-all-4.4.0-source-release.zip），在弹出页面选择红框内的镜像链接。
2、将压缩包保存到/opt/RocketMQ并解压
3、在控制台下依次输入下面代码，最终路径：/opt/RocketMQ/rocketmq-all-4.4.0/distribution/target/apache-rocketmq
cd /opt/RocketMQ/rocketmq-all-4.4.0
mvn -Prelease-all -DskipTests clean install -U
cd distribution/target/apache-rocketmq4、启动nameServer，在控制台依次输入
nohup sh bin/mqnamesrv &
tail -f nohup.out如果控制台显示以下信息（3）则说明启动成功
注意：可能在运行的时候会报错：
Java HotSpot(TM) 64-Bit Server VM warning: Using the DefNew young collector with the CMS collector is deprecated and will likely be removed in a future release
Java HotSpot(TM) 64-Bit Server VM warning: UseCMSCompactAtFullCollection is deprecated and will likely be removed in a future release.
Java HotSpot(TM) 64-Bit Server VM warning: MaxNewSize (4194304k) is equal to or greater than the entire heap (4194304k). A new max generation size of 4194240k will be used.
Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x00000006ec800000, 2147418112, 0) failed; error='Cannot allocate memory' (errno=12)
#
# There is insufficient memory for the Java Runtime Environment to continue.
# Native memory allocation (mmap) failed to map 2147418112 bytes for committing reserved memory.
# An error report file with more information is saved as:
# /opt/RocketMQ/rocketmq-all-4.4.0/distribution/target/apache-rocketmq/hs_err_pid3162.log
主要原因是启动nameserver默认的最小内存是4个g，但是服务器内存不足（我起的是虚拟机，只分配了2G的内存）。所以要修改nameserver的配置文件（runserver.sh）。（启动broker的时候可能也会因为这个原因报错，具体操作差不多，只不过是修改runbroker.sh）
修改/opt/RocketMQ/rocketmq-all-4.4.0/distribution/target/apache-rocketmq/bin/runserver.sh文件，修改内存分配，然后再次启动。
5、启动broker，在控制台依次输入：
nohup sh bin/mqbroker -n localhost:9876 &
tail -f nohup.out如果控制台出现红框内容，则说明启动成功，红框上面的是刚刚启动nameserver时的信息。
注意：除了出现上面说的启动broker时内存不足，还可能出现无法识别主机名：
java.net.UnknownHostException: czz.centOS: czz.centOS: Name or service not known
at java.net.InetAddress.getLocalHost(InetAddress.java:1506) ~[na:1.8.0_201]
at org.apache.rocketmq.common.BrokerConfig.localHostName(BrokerConfig.java:185) [rocketmq-common-4.4.0.jar:4.4.0]
at org.apache.rocketmq.common.BrokerConfig.<init>(BrokerConfig.java:38) [rocketmq-common-4.4.0.jar:4.4.0]
at org.apache.rocketmq.broker.BrokerStartup.createBrokerController(BrokerStartup.java:110) [rocketmq-broker-4.4.0.jar:4.4.0]
at org.apache.rocketmq.broker.BrokerStartup.main(BrokerStartup.java:58) [rocketmq-broker-4.4.0.jar:4.4.0]
Caused by: java.net.UnknownHostException: czz.centOS: Name or service not known
at java.net.Inet6AddressImpl.lookupAllHostAddr(Native Method) ~[na:1.8.0_201]
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:929) ~[na:1.8.0_201]
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1324) ~[na:1.8.0_201]
at java.net.InetAddress.getLocalHost(InetAddress.java:1501) ~[na:1.8.0_201]
... 4 common frames omitted
解决方法：在控制台输入
vi /etc/hosts在后面添加一条主机信息。由于我的主机名是czz.centOS，所以我添加。保存后再次启动broker
6、使用jps查看是否启动成功
7、关闭nameserver broker执行的命令
#官方建议先关闭broker，因为broker依赖nameserver
sh bin/mqshutdown broker
#再关闭nameserver
sh bin/mqshutdown namesrv8、验证是否能够生产和消费消息，依次输入以下代码
生产消息：
#设置名称服务地址
export NAMESRV_ADDR=localhost:9876
#投递消息
sh bin/tools.sh org.apache.rocketmq.example.quickstart.Producer
结果：
消费消息：
#消费消息
sh bin/tools.sh org.apache.rocketmq.example.quickstart.Consumer
结果：
官方文档：http://rocketmq.apache.org/docs/quick-start/
控制台安装可以参考：https://blog.csdn.net/chenzz2560/article/details/90238769后面的教程