Diego Freniche

Maybe this helps...

You need to know which executable is fired when you type "javac -version". The "which" command comes to rescue:
dfreniche@tesla:~$ which javac /usr/bin/javac
So now we know that /usr/bin/javac is the one that "answers" our keystrokes. Is it a real program or a symlink?
dfreniche@tesla:~$ ls -al /usr/bin/javac lrwxrwxrwx 1 root root 23 2007-12-28 13:21 /usr/bin/javac -> /etc/alternatives/javac
What! Is a symlink! Lets ls again:
dfreniche@tesla:~$ ls -al /etc/alternatives/javac lrwxrwxrwx 1 root root 37 2007-12-28 13:21 /etc/alternatives/javac -> /usr/lib/jvm/java-1.5.0-sun/bin/javac
So probably the /etc/alternatives/javac link will point to the not desired javac. Change it (as root) using:
ln -sf <the-right-javac-program> /etc/alternatives/javac

Maybe you installed Eclipse using synaptic (as an Ubuntu Package)? I'd rather prefer to unpack the tgz off the Eclipse web in /opt. This way I control Ubuntu. And soon the rest of the world. BWUAHAHAHAHAHAHAH! ;-)

Originally posted by Gregg Bolinger:


I didn't know about that. Cool! Thanks Jesper.

If you want to have a look under the hood, try:
ls /etc/alternatives
You can change a symbolic link by hand :-)

I always install various JDKs in /opt. Later, I use different environment variables (or configs inside Eclipse) to point to one JDK or another.

We are shifting an application from one production server to the other DCC(Data Center Consolidation) environment .
So we have all Unix boxes. so for migrating the stuff we need unix shell scripting stuff

Have all machines the same UNIX OS? I mean, are they Linux, Solaris, HP-UX ? And most important, which UNIX Shell are you using, bash, sh, tcsh, csh, ...?
I know if this is your first UNIX-scripting time it's a hard time, but you'll learn things that haven't changed for ages. And you will learn tricks that you can use on your Windows boxes also (f.e., shutdown command, tab to complete filenames in cmd windows, symbolic links in NTFS, ...)

If you're using bash, try searching Google for bash course, bash book, or similar. A good web, but a little bit advanced, is: http://bashcurescancer.com/

There I found: http://www.pixelbeat.org/cmdline.html

But maybe you'll value http://www.freetechbooks.com/about180.html&highlight=bash

Kind regards, and go 4 it! It's always exciting to learn new things!

Time to think...
If you boot on the Windows side, everything is OK, DHCP works, you get an IP address from your US Robotics 8004 Router, and life's good :-)
So I assume:
- dhclient in Windows works OK.
- you have DHCP server active on your US Robotics 8004, and you can log into the router and see which computers have obtained as IP.

If that fails in Linux, but setting a static IP works, then it's one of two:
- you have connected at the same time the ethernet cable AND your wifi card (if the machine is a laptop). Disconnect wifi and try only with ethernet UTP cable.
- your /etc/network/interfaces is not correctly configured. Try:
auto eth0 iface eth0 inet dhcp
Save, and then:
/etc/init.d/networking restart

Hope this helps

Think of it that way:
- JVM: Java Virtual Machine. The program that interpretes Java bytecode stored in .class files. In Windows, java.exe.
- JRE: Java Runtime Environment. A JVM is not enough. You need an implementation of the core Java APIs. As you need in C the shared libraries installed in your system.

In short:
JRE = JVM + core Java APIs (in jar format) + utils

Install "filelight", a wonderful app that shows you used space graphically.
Just go to a root console and try:
apt-get install filelight
or better, use Synaptic package manager.

<Disclaimer>
This info apply to Debian Linux, and it should work more or less on RH / Fedora, buy YMMV.
</Disclaimer>

Test your IP stack is working. Open a console, an become root using:
$ su
When root passord is entered, your prompt will change to #
Then, write:
# ifconfig
You will see information for every network interface installed in your machine. It tipically starts with interface lo (local) AKA 127.0.0.1. eth0 is your first ethernet card, eth1 the 2nd, etc. Wifi cards must appear also.

Can you see eth0 here: OK.
If not, your network card kernel module (is not exactly the same, but view it as a "driver") is not loaded. Post here and will try to help.

If you can see the network card, try using a graphical config program or, better, go to /etc/network and assign yourself an static IP. Edit file interfaces as root:
# kate /etc/network/interfaces
It should look kind of:
allow-hotplug eth0 auto eth0 iface eth0 inet static address 192.168.109.161 netmask 255.255.0.0 gateway 192.168.100.3

Obviously, you will have to adjust IP ranges, gateway Ip and so on.
Restart network using: /etc/init.d/networking restart.

I found the Java language easy to learn (I was proficent in both C/C++ and VB) but the techno-buzz and the cumbersome number of java products made it a hard time.
Once you know Java, you face Chaos:
- may I learn how to make Applets sing and dance?
- How about Swing / AWT? Not to mention SWT from Eclipse...
- Obviously, I need to learn every construct of the Java languaje, now.
- Object relational mapping: Hibernate, Entity EJB, OJB, ...
- What IDE is better: Eclipse, NetBeans, ...
- plus other 1024 random questions.
That's what I advice:
- Learn how to make console Java apps. Learn the basics. Avoid reading a line on Applets. If you are not going to make any desktop apps, jump the AWT / Swing chapters.
- Skip streams / files. Skip socket programming.
- Learn OOP in Java. Learn JDBC. Learn the basic APIs: java.util, the Wrapper classess, etc.
- Buy a book on servlets / JSP.
- Learn an Object - Relational mapping package. Hibernate is relatively easy to learn.
- Focus on MVC: Struts is easy to learn.
- From here, go to JSF and Spring.

I know it's a stupid advice, but don't get stressed. You will need at least two years to master all that stuff. So take it easy...