Hello all-
I'm new with installing programs on linux and I have some questions hopefully someone can help me out with. I'm trying to install Java SDK so I can do some programming assignments at home. After following the install instructions I was under the impression I could use some commands like javac, java, etc. I keep getting command not found errors though. So I checked several things:
1.I looked in /var/lib/rpm: java sdk wasn't in there.
2. Next I tried these commands to uninstall and then reinstall:

try to remove it so i can reinstall:
rpm -e j2sdk-1_4_2_05-linux-i586.rpm
error: package j2sdk-1_4_2_05-linux-i586.rpm is not installed

try to install:
rpm -iv j2sdk-1_4_2_05-linux-i586.rpm
Preparing packages for installation...
package j2sdk-1.4.2_05-fcs is already installed
I executed these commands one right after the other. How is it possible that this can be correct? Basically from my understanding it is saying that j2sdk is not installed, and that it is installed. Does anyone know what I'm doing wrong? Thanks in advance for any help.

you don't use the rpm filename to uninstall. you need to use the package name.

try:

rpm -e j2sdk

if you need to be more exact with the package name, use:

rpm -qa | grep j2sdk

the output is the exact package name for the java sdk that you can use 'rpm -e' on.

okay, before you read the rest of this, try typing "source /etc/profile" into a shell. now does java or javac give you any output? if so, cool. if not...

I'm not sure about package management for your specific distro, but try this:

as root:
(it'll take about 5 minutes -- it builds a database of everything on your system, which will make future file searching fast)

then,
Note: if you don't have root access on the machine, you can always run
but it's sloooooow...

anyway, let's say it found java in /opt/sun-jdk-1.4.2_05/bin/javac
then you want your JAVA_HOME to be /opt/sun-jdk-1.4.2_05

if it was found in /usr/local/bin, on the other hand, ignore the rest of this, and simply add /usr/local/bin to your PATH variable.

Now that you know where java is, open up your .bashrc file in a text editor (assuming you're using bash. type "echo $SHELL" to find out your shell, and if it's csh, edit .cshrc, and likewise).

add the following lines to the file:
export JAVA_HOME=/path/we/just/discussed
export PATH=$PATH:$JAVA_HOME/bin

Thanks for all the help. I got it all worked out now.
I have one other question maybe someone can explain for me. I found a tutorial about how to edit /etc/profile.d/java.sh. I created that file and put the location of java in for my PATH variable. What I was wondering is if you have to do that for each program you install, or if I should just try to install all of my programs in one of the paths already set up in PATH. Thanks again.

java is one of the only things i know of that requires editing of the profile script to get the path set. i personally like to use pathmunge for setting the java path globally for all users.

but aside from java, other compilers might require you to set the path so you can use the unqualified program name (start program without having to specify a fully qualified path to the executable). i set up the path for intel's c++ compiler the same way i set it up with java.

but for regular, non-compiler programs, if you compile the programs from source and the program uses configure script in it's install process, you won't usually need to set the path for using it by using the correct path for the --prefix option. it basically depends on where you install the software at, since linux has some predetermined locations to search through.