If a package is available on your Red Hat Linux or Fedora Core CDROM, there's an Add/Remove Applications application that is useful. It is invoked via,
Main Menu --> System Settings -->
It will ask you for the root password, and once that is provided, it will display all applications that may be installed. Once you have ticked the applications that you want installed, you just need to click "Update" to install. Change the discs as you are prompted, and once this is done, you will have the software installed.
However, in the open source world where applications change quite often, and fixes are posted, this method might mean you get out-dated software. This is where tools like yum and apt come into play.
To search the yum database for a piece of software, you can invoke,
# yum search xargs
where xargs is an example of an application that needs to be installed. Yum will report if it finds xargs, and if its successful, performing,
# yum install xargs
will be all that is required. If xargs calls for any dependencies, it will be resolved automatically, and those packages get pulled in automatically too.
This is similar with Debian and apt.
# apt-cache search xargs
# apt-get install xargs
If you want to install a downloaded RPM or DEB file manually, it can be performed like,
# rpm -ivh xargs.rpm
# dpkg -i xargs.deb
And if you're manually upgrading a package, use,
# rpm -Uvh xargs.rpm
The above command will upgrade the package if it is already installed or install it if it is not. To perfrom an upgrade only if the package is curently installed, use,
# rpm -Fvh xargs.rpm
There are many more options to pass to the rpm, dpkg, yum, apt-get and apt-cache tools, and the best way to learn more, would be to read their manual pages. It is also worthy to note that apt-get is available for RPM-based systems, so versions for Red Hat Linux or Fedora Core (or even SuSE or Mandrake) are available as a download from the Internet.
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Linux Tutorial: Packaging, Updating, and Installing
2. Keeping Up-To-Date
3. Installing New Packages