The difference between jre / jre-1.7.0 / jre-1.7.0-openjdk / jre-openjdk /jre-1.7.0-openjdk-1.7.0.261-2.6.22.2.el7_8.x86_64 [closed]

1. My Query & what I reseached

After I installed JDK for Linux X64 (8u181-b13), the directory of /usr/lib/jvm included the following symbolic link of jre's.

Terminal Screenshot

lrwxrwxrwx   1 root root   21 May 29  2020 jre -> /etc/alternatives/jre  lrwxrwxrwx   1 root root   27 May 12  2020 jre-1.7.0 -> /etc/alternatives/jre_1.7.0  lrwxrwxrwx   1 root root   35 May 12  2020 jre-1.7.0-openjdk -> /etc/alternatives/jre_1.7.0_openjdk  lrwxrwxrwx   1 root root   54 May 12  2020 jre-1.7.0-openjdk-1.7.0.261-2.6.22.2.el7_8.x86_64 -> java-1.7.0-openjdk-1.7.0.261-2.6.22.2.el7_8.x86_64/jre  lrwxrwxrwx   1 root root   27 May 12  2020 jre-1.8.0 -> /etc/alternatives/jre_1.8.0  lrwxrwxrwx   1 root root   35 May 12  2020 jre-1.8.0-openjdk -> /etc/alternatives/jre_1.8.0_openjdk  lrwxrwxrwx   1 root root   51 May 12  2020 jre-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64 -> java-1.8.0-openjdk-1.8.0.252.b09-2.el7_8.x86_64/jre  lrwxrwxrwx   1 root root   29 May 12  2020 jre-openjdk -> /etc/alternatives/jre_openjdk  

My query what is the difference of these versions, and which should be specifed during installation of Tomcat8.5.55 .

jre  jre-1.7.0  jre-1.7.0-openjdk  jre-1.7.0-openjdk-1.7.0.261-2.6.22.2.el7_8.x86_64  jre-openjdk  

As far as I searched, my understanding of each sybolic link as follows.

jre

-Is a sybolic link pointing to

/etc/alternatives/jre  

-It is only including JRE and does not include JDK

-The difference I found from jre-1.7.0 and jre-1.8.0 is that this jre is including "jjs" which is a javascript library which is depreciated now

jre-1.7.0

-Is a sybolic link pointing to

/etc/alternatives/jre_1.7.0  

-It is only including JRE and does not include JDK

jre-1.7.0-openjdk

-Is a sybolic link pointing to

/etc/alternatives/jre_1.7.0_openjdk  

-It is only including JRE and does not include JDK, only installing the JRE part from the open JDK.

jre-openjdk

-Is a sybolic link pointing to /etc/alternatives/jre_openjdk

-It is an open source implementation of JavaSE and this includes JDK.

2. Background of query & What I want to do

I am now trying to install Tomcat 8.5.55 in CentOS 7.I am asking this question because, when I create tomcat service file, there is a line which specifies the JAVA_HOME, and I couldn't figure out whether to give "jre" or "jre-1.7.0" or "jre-1.8.0" in this path.

Environment=JAVA_HOME=/usr/lib/jvm/jre  

[Entire tomcat.service file]

# Systemd unit file for tomcat  [Unit]  Description=Apache Tomcat Web Application Container  After=syslog.target network.target     [Service]  Type=forking     Environment=JAVA_HOME=/usr/lib/jvm/jre  Environment=CATALINA_PID=[Tomcat Home Directory]/temp/tomcat.pid  Environment=CATALINA_HOME=[Tomcat Home Directory]  Environment=CATALINA_BASE=[Tomcat Home Directory]  Environment='CATALINA_OPTS=-Xms512M -Xmx1024M -server -XX:+UseParallelGC'  Environment='JAVA_OPTS=-Djava.awt.headless=true -Djava.security.egd=file:/dev/./urandom'     ExecStart=[Tomcat Home Directory]/bin/startup.sh  ExecStop=/bin/kill -15 $MAINPID     User=tomcat  Group=tomcat  UMask=0007  RestartSec=10  Restart=always     [Install]  WantedBy=multi-user.target  

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https://stackoverflow.com/questions/65860318/the-difference-between-jre-jre-1-7-0-jre-1-7-0-openjdk-jre-openjdk-jre-1 January 23, 2021 at 10:26PM