CentOS下把Tomcat安装配置成系统服务方便重启、开机启动

Tomcat从官网下载后，是个压缩包，解压后如果没有特别的设置，启动和重启Tomcat的时候需要到Tomcat目录下的bin下启动，也不方便弄成开机启动，安装成服务后，就都可以实现了。

1. 安装OracleJDK 或者OpenJDK

   # download rpm from: https://www.oracle.com/java/technologies/javase-downloads.html
   rpm -ivh jdk-11.0.9_linux-x64_bin.rpm
   
   #check java version
   java -version

2. 添加tomcat用户

   sudo groupadd tomcat
   sudo useradd -M -s /bin/bash -g tomcat -d /home/tomcat tomcat

   可根据实际情况看tomcat是否需要可以登录，如果不需要登录，执行usermod tomcat -s /sbin/nologin

3. 下载Tomcat http://tomcat.apache.org/

   cd /opt
   wget https://downloads.apache.org/tomcat/tomcat-9/v9.0.40/bin/apache-tomcat-9.0.40.tar.gz
   tar zxvf apache-tomcat-9.0.40.tar.gz
   ln -s apache-tomcat-9.0.40 tomcat
   
   #change permission
   chmod +x /opt/apache-tomcat-9.0.40/bin/*.sh
   chown -R tomcat: /opt/apache-tomcat-9.0.40
   chown -R tomcat: /opt/tomcat
   #把tomcat/work下的目录权限改成777，发现有时候tomcat起不来，报错：java.lang.IllegalStateException: No output folder
   #改了如下权限就好了
   chmod -R 777 /opt/tomcat/work

4. 安装服务相关：
   
   编辑文件 vim /etc/systemd/system/tomcat.service

   [Unit]
   Description=Tomcat 9 servlet container
   After=network.target
   
   [Service]
   Type=forking
   
   User=tomcat
   Group=tomcat
   
   Environment="JAVA_HOME=/usr/lib/jvm/jre"
   Environment="JAVA_OPTS=-Djava.security.egd=file:///dev/urandom"
   
   Environment="CATALINA_BASE=/opt/tomcat"
   Environment="CATALINA_HOME=/opt/tomcat"
   Environment="CATALINA_PID=/opt/tomcat/temp/tomcat.pid"
   Environment="CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC"
   
   ExecStart=/opt/tomcat/bin/startup.sh
   ExecStop=/opt/tomcat/bin/shutdown.sh
   
   [Install]
   WantedBy=multi-user.target
   
   

   检查下以上文件内容，里面的变量和自己的系统是否一致，
   如果Oracle的JDK可能是:
   JAVA_HOME=/usr/java/default
   CATALINA_OPTS的参数根据自己的机器调整Xmx的数据可以是自己机器内存的3/4
   

   关于tomcat内存的调整，详见：https://blog.terrynow.com/2021/10/10/tomcat-startup-with-memory-options-to-avoid-out-of-memory-error-or-make-full-use-of-memory/

5. 服务相关操作

   #使新安装的tomcat服务生效
   systemctl daemon-reload
   #开机启动tomcat
   systemctl enable tomcat
   #启动tomcat
   systemctl start tomcat
   systemctl status tomcat
   systemctl restart tomcat