This great explanation about the way of software installation in (SAM-)Linux is copied from a user´s post at the SAM Linux forums:
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If you are coming from a windows world, installing programs (though arguably easier) is probably one of the most bizarre things about moving to Linux.
Here's my noobish explanation on how the process differs.
Generally, with Windows, the only software you can get your hands on has already been compiled, and it's often compiled such that it will run on most or multiple versions of windows, it's usually packaged in an installer (setup.exe/setup.msi or similar) that includes any dependencies (other files or libraries needed by the software you are installing)
The install process is, if not hidden from the user, at least not especially transparent, since there are usually files that go not only to *:\Program Files\Whatever, but also often things added to *:\Windows, *:\Windows\System32, or a number of other locations, plus information added to the registry.
Linux installations (on all the distros I've tried, and despite my general lack of expertise there have been many) usually seem to go differently. Even though different distributions of Linux have a great many similarities, it's generally best to get a package for a given application that has been compiled just FOR that distribution. Exceptions are things like SAM, which (AFAICT) uses PCLOS packages natively, since PCLOS is the foundation for SAM. My understanding is that the various *ubuntu distros are more of a grey area, since they can in some cases use debian packages, and other times not. Zenwalk often used slackware packages, etc…
The repositories in Synaptic (should be 5th icon from left in a default SAM install) will show you all the software that has been precompiled for SAM (and presumably tested to some degree) and provided by the SAM team.
Synaptic is also your tool for keeping your system updated, as you can see if you play with the different filters/categories.
*Always click "Reload" before doing anything in Synaptic. This will update the lists of repository contents locally.*
You'll probably find that the vast, vast majority of anything you hear about or want is already there.
When you use Synaptic to mark and install a package, it will do the legwork of checking out what other applications or libraries are required — and will also install those for you.
One nice thing about Linux is that installing something doesn't splash files all over the place like in Windows. There are a small number of specific locations where things get installed — and I'm too much of a noob to tell you where those places are. smiley
Installation should generally be the reverse of removal, using Synaptic.
If you find something that you want that is NOT available for you in Synaptic, it will probably have instructions at the applicable web page telling you how to compile it for yourself, and install it. This is apparently simple to people who do it all the time — I've only done it once or twice. (But it wasn't that bad.) Should that happen, I'd recommend you post here to get input from some of the more knowledgeable people around. The important point is that just because it isn't in Synaptic from the repositories does NOT mean you can't get it. You can, and it's probably not that hard. Synaptic should be the preferred route if possible, however. If something you want is a common request, you might just be the guy who gets them to start including it in the repositories — which is nice because some knowledgeable guru does the compiling/testing/etc, and they'll probably then keep it updated as well.
One other neat thing — most of the executable names are the same (or very similar to) the program names. Can't find a shortcut? Just type the name of any installed program into the "run program" box, and it will probably work.
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