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Browser -> httpd -> Tomcat -> MySQL. Restarting.

I've just completed a course covering the installation and configuration of Apache httpd, Apache Tomcat and MySQL. Complete with a demonstration that has the newly installed systems visited from various browsers, talking to httpd, which talks on to Tomcat, which talks on in turn to MySQL. The MySQL responses are handled by the Servlets and JSPs running on Tomcat, and returned via the masking Apache httpd that's used for the majority of the web site on the chosen domain. This might all sound very complicated, but it's actually what happens on so many web sites which, no doubt, is why there's such a call for our deployment course.

And what happens when the server is restarted? Well - you had better make sure that all the services start up properly, hadn't you?

On a Linux / Unix system, you can add scripts that are to be run during system startup, typically to start server processes known as daemons, to the directory /etc/init.d. These scripts should understand (as a minium) a command line parameter "start" to do everything needed to start the service, and "stop" to do everything needed to stop the service. And it's no coincidence that modern versions of apache httpd ship with a utility called apachectl that accepts these argument, apache tomcat ships with catalina.sh which also accepts these parameters, and there'a a utility script in mysql's script directory that does the same thing for that daemon.

So it that all you need to know? Not quite! Just placing the scripts into /etc/init.d does NOT cause them to be run; on system startup, when entering full multi-user mode (run state 3) or multiuser mode with windows (run state 5), Linux / unix go through the directory /etc/rc3.d (or rc5.d, or /etc/init.d/rc3.d etc ... depending on the Linux flavour) and run every file starting with the letter S in asciibetic order. Now - you do not want to copy the scripts from init.d to those other directories so the whole thing is set up by filling the "rc" directories with a series of symbolic links back to /etc/init.d. That way, you can turn daemons on and off just by adding and removing links - a very neat scheme indeed.

Here's an example of such a link in /etc/init.d/rc3.d (on a SuSE system)

lrwxrwxrwx 1 root root 10 2006-10-27 14:38 S19apache2 -> ../apache2

and that could be set up by a command such as

ln -s ../apache2 apache2

of using the chkconfig utility that's provided to help with tasks such as this ... but that's an extended story for another day!
(written 2006-10-28, updated 2009-01-01)

 
Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles
A164 - Web Application Deployment - Services and Regular Jobs
  [4487] Starting MySQL. ERROR! The server quit without updating PID file - how we fixed it. - (2015-05-06)
  [3792] Managing daemons from a terminal session - (2012-07-01)
  [3791] The Kernel, Shells and Daemons. Greek Gods in computing - (2012-07-01)
  [3143] On time - (2011-01-23)
  [3011] What are .pid files? - (2010-10-23)
  [2182] What Linux run level am I in? - (2009-05-15)
  [2145] Using the internet to remotely check for power failure at home (PHP) - (2009-04-29)
  [1903] daemons - what is running on my Linux server? - (2008-11-23)
  [1765] Dialects of English and Unix - (2008-08-21)
  [1733] memcached - overview, installation, example of use in PHP - (2008-08-02)
  [1731] Apache httpd, MySQL, PHP - installation procedure - (2008-08-01)
  [1700] FTP server on Fedora Linux - (2008-07-06)
  [1633] Changing a screen saver from a web page (PHP, Perl, OSX) - (2008-05-06)
  [1553] Automatic startup and shutdown of Tomcat - (2008-02-24)
  [1288] Linux run states, shell special commands, and directory structures - (2007-08-03)
  [1028] Linux / Unix - process priority and nice - (2007-01-10)
  [544] Repeating tasks with crontab - (2005-12-27)

A602 - Web Application Deployment - Apache httpd - Sourcing, Installation, Testing
  [4437] Adding a PHP build option, rotating an image based on camera data, and a new look at thumbnails in PHP - (2015-02-22)
  [3426] Automed web site testing scripted in Ruby using watir-webdriver - (2011-09-09)
  [2520] Global and Enable - two misused words! - (2009-11-30)
  [2184] Choosing the right version of Java and Tomcat - (2009-05-16)
  [2096] Where is my new Apache httpd installed - (2009-03-22)
  [2080] Using ApacheBench and jconsole to test and monitor Tomcat - (2009-03-14)
  [1945] Summary - Apache httpd build on Linux - (2008-12-14)
  [1768] What is built in to this httpd and PHP? - (2008-08-23)
  [1707] Configuring Apache httpd - (2008-07-12)
  [1455] Connecting to MySQL 5 from PHP on Mac OSX Leopard - (2007-12-03)
  [1449] Upgrade Mac OSX to Leopard, Web Server Apache httpd config lost - (2007-11-29)
  [1292] DHCP automatic IP address v Static IP - (2007-08-06)
  [1095] Apache httpd , browser, MySQL and MySQL client downloads - (2007-02-28)
  [982] Notes from the white board - (2006-12-14)
  [660] Stopping and restarting Apache httpd cleanly - (2006-03-29)
  [550] 2006 - Making business a pleasure - (2006-01-01)
  [526] Apache httpd - serving web documents from different directories - (2005-12-12)
  [523] Apache httpd release 2.2 - (2005-12-10)

A654 - Web Application Deployment - Configuring and Controlling Tomcat
  [3043] Gathering information - logging - with log4j. First steps. - (2010-11-12)
  [2652] Reading and writing cookies in Java Servlets and JSPs - (2010-02-26)
  [2163] CATALINA_OPTS v JAVA_OPTS - What is the difference? - (2009-05-09)
  [2061] Tomcat 6 - Annotated Sample Configuration Files - (2009-03-01)
  [2039] The Invoker - (2009-02-13)
  [1994] tomcat-users.xml; what a difference a space made - (2009-01-16)
  [1943] Port and Glasses - (2008-12-14)
  [1762] WEB-INF (Tomcat) and .htaccess (httpd) - (2008-08-20)
  [1503] Web page (http) error status 405 - (2008-01-12)
  [1370] Apache Tomcat Performance Tuning - (2007-09-29)
  [1351] Compressing web pages sent out from server. Is it worth it? - (2007-09-14)
  [914] A practical example of roles - (2006-11-04)
  [837] Tomcat - Shutdown port - (2006-08-18)

S153 - Sourcing, Running and Configuring MySQL
  [4406] Fixing damaged MySQL tables - Error 1712 and Error 2013 - (2015-01-25)
  [4390] Checking MySQL database backups have worked (not failed) - (2015-01-10)
  [2458] Cant connect to local MySQL server through socket /tmp/mysql.sock - (2009-10-17)
  [2445] Securing MySQL on a production server - (2009-10-09)
  [2444] Potted MySQL installation - (2009-10-09)
  [2426] Which version of MySQL am I running? - (2009-09-26)
  [2209] Monitoring and Tuning your MySQL installation - (2009-05-31)
  [2085] MySQL - licensing issues, even with using the name - (2009-03-16)
  [1935] Summary of MySQL installation on a Linux system - (2008-12-11)
  [1771] More HowTo diagrams - MySQL, Tomcat and Java - (2008-08-24)
  [1689] Some sideways thoughts on the news - (2008-06-27)
  [1131] MySQL - Password security (authentication protocol) - (2007-04-02)
  [1123] mysqldump and mysqlrestore - (2007-03-30)
  [591] Key facts - SQL and MySQL - (2006-02-04)
  [535] MySQL permissions and privileges - (2005-12-20)
  [515] MySQL - an FAQ - (2005-12-03)
  [489] Which MySQL server am I using? - (2005-11-07)
  [334] Symbolic links and hard links - (2005-06-02)
  [192] Current MySQL and PHP paths and upgrades - (2005-01-28)


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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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