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Whole description of the module:
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The module reads configuration files of tomcat and webapps:
  /etc/tomcat6/server.xml
  /etc/tomcat6/web.xml
  /etc/tomcat6/context.xml
  /etc/tomcat6/tomcat-users.xml
  /usr/share/tomcat6/webapps/*/WEB-INF/web.xml
  /usr/share/tomcat6/webapps/*/WEB-INF/context.xml

and check them for incompatibilities mentioned in:
  https://tomcat.apache.org/migration-7.html#Java_6_required

See solutuionTexts in check.py script, for better understanding. However
briefly (post below means post-upgrade script something does):

- check & modifications of XML files
  - when "manager" or  "admin" roles exist (tag rolename in role)
     - solution text + medium risk + exit failed
     - post: modify
         admin -> admin-gui
         manager -> manager-gui
       result is not fixed because behaviour can be different
  - when attrib "randomClass" in "Manager" is used
     - solution + log info + exit fixed
     - post: modify
         randomClass -> secureRandomClass
  - when attrib "emptySessionPath" in "Connector" is used
     - log medium risk + exit failed
     -post:  remove attrib from a tag
  - when attrib "disableURLRewriting" in "Context" is used:
     - solution + medium risk + exit fail
     - post: remove an attrib from a tag
  - when "param-name" of a "servlet" contains "genStrAsCharArray":
     - solution + log info + exit fixed
     - post: modify
         genStrAsCharArray -> genStringAsCharArray
  - when "Host" or "Context" contain a "copyXML" attrib:
     - solution + medium tisk + exit failed

  - when "allow", "deny", "internalProxies" or "trustedProxies"
    are set as attrib of Valve or set inside servlet (see
    "init-param" in /etc/tomcat6/web.xml):
    - solution + log high risk + exit failed
      (each of them can be logged max. once per file)

  - when attrib "filter" is used in "Valve":
    - solution + log high risk + exit failed
      (logged once per file)

  - when attribs "restrictedUserAgents" or "noCompressionUserAgents"
    are used in "Connector":
    - solution + log high risk + exit failed

- check script in addition:
  - copy post-upgrade script "post-tomcat.py" into
  "<postupgrade dir>/services/tomcat/" with all relevant files to run the
  postcript correctly and set the file executable
    - in the same directory, create file "packages" that contains tuples
      <native-installed-tomcat6-pkg>|<new-tomcat-pkg>
  - store diff between current server.xml file and default server.xml file
    into the default_diff.diff file inside current working directory
    (probably "/root/preupgrade/RHEL6_7/services/tomcat/")
    NOTE: maybe will be printed to output or stored into different directory
  - when "tomcat" package is installed (tomcat != tomcat6) - probably from EPEL
    or 3rd party:
     - solution + log high risk + copy "remove-tomcat-pre-upgrade.sh" into:
        "/root/preupgrade/preupgrade-script/"
       - the script blocks inplace-upgrade during pre-upgrade phase of rhelup
         when tomcat package is installed

- post upgrade script in addition:
   - install new rpms according to info in "packages" file
   - move original tomcat6 configs to the new path
   - move original webapps to the new path
     (/usr/share/tomcat/webapps directory is backed up (moved) with suffix
     "-preupg-backup" prior the move of tomcat6 webapps)

