help me understand YUM

[flguy2]

Hello. I am all new to Linux. I'm experimenting with Amazon's EC2 service and so I'm working with one of their public Fedora Core 4 images.

I went to install FFMPEG using YUM based on some random instructions I found on the internet, and it all worked!!! Great. Except I have no idea WHY it worked. I would like to how/why/where YUM knew to install FFMPEG.

Here are the instructions I followed:

1) rpm -ivh http://ftp.freshrpms.net/pub/freshrp....fc.noarch.rpm

2) yum update

3) yum install ffmpeg

And it just worked. My questions are: 1) what is freshrpms and what does it have to do with ffmpeg, 2) what is yum "updating", 3) how does yum know where to get ffmpeg, 4) how do I know it got the lastest version of ffmpeg?

Because I am coming from the Windows world I basically expected to download an FFMPEG file (which I did actually) and then point YUM to that package I downloaded. But I never had to do that. By following the 3 steps above FFMPEG just magically installed and I am disturbed by the fact that I don't know how or why!

Any insights for this newbie would be wonderful. Thanks.

[Thrillhouse]

It's good that you want to know what's going on. Linux users are curious by nature.

My questions are: 1) what is freshrpms and what does it have to do with ffmpeg,

Freshrpm's is a third party repository that can be used with yum. yum is Fedora's package manager. Packages are software, basically. If you want to install something, you have to install its package. However, that package may depend on other packages that need to be installed along with it. That's what yum is for. yum handles the installing of that package, along with all of its dependencies, so you don't have to go about installing them individually. yum fetches these packages from package repositories on the Internet. Fedora has its own, official repository containing all of the packages that it supports but because Fedora is a distribution that believes 100% in free software, they don't include any packages that would provide support for a proprietary codec. I'm assuming you installed ffmpeg to try and get mp3's to work. Well, mp3 (along with wmv, java, flash, etc.) is a proprietary format. Therefore, Fedora, itself won't support it but you can get packages for it from 3rd party repositories like freshrpm's. Livna is another third party repository that provides pretty much the same things freshrpm's does.

2) what is yum "updating",

When you run "yum update" you're asking yum to go out and check the repositories to see if there are any newer versions of packages that you have installed on your machine. If there are newer versions, yum will download them and replace the older version with the newer version.

3) how does yum know where to get ffmpeg,

You told yum where to get it in the first command. That first command imported the freshrpm's repository and changed your repository configuration to include it.

4) how do I know it got the lastest version of ffmpeg?

Running yum update periodically (daily, is a good practice) will check freshrpm's for any new versions of it. Repositories always contain the latest package. Older packages are archived sometimes if you want to install a specific version but the repositories are kept up to date with the latest and greatest packages.

Because I am coming from the Windows world I basically expected to download an FFMPEG file (which I did actually) and then point YUM to that package I downloaded. But I never had to do that. By following the 3 steps above FFMPEG just magically installed and I am disturbed by the fact that I don't know how or why!

Well, do you understand what happened now?

Welcome to Linux.

[T3ddy]

1) Freshrpms is a place where you can find all sorts of software and/or libraries in the RPM format. They don't have anything directly to do with FFMPEG, they just offer a place to find/download software/libraries.

2) Yum checks with a server to see whether there are any more up-to-date versions of any programs you have installed. If it finds any, these are automatically downloaded and installed.

3) There are YUM servers that have all the software on them as well as information about the package, like which version it is. Basically, you don't need to know how YUM works. That's the point. You just tell it what you want and it downloads and installs it automatically.
4) yum list <package_name>. You should then get information on the version like "FFMPEG2.428". You can then check with the software website to see if it's the most up-to-date version. However this is almost never necessary. Yum keeps stuff pretty up-to-date.

for full information on YUM: Fedora Project, sponsored by Red Hat

[flguy2]

This is wonderful, exactly the kind of insight I needed. Perhaps YUM is just simpler than I can believe right now, and this is why people leave Windows.

[flguy2]

Sorry, I have another related question. Th web site below seems to be explaining how to manually install ffmpeg. Why would someone want to do this if you can just yum it? What's the difference, if any? This actually looks a little more familiar to me coming from a Windows world.

vexxblog » ffmpeg

[Thrillhouse]

Why would someone want to do this if you can just yum it?

That's the kind of thinking that sparked the ideas for package managers. The method described in that tutorial is called compiling from source. It's another method of installing software but, as you can see, is a little more complicated. rpm packages, like the ones used in Fedora, are pre-compiled so you don't have to go through that trouble. There are other package formats besides rpm like deb. They are all different but are built around the same concept: making it easier to install software.

What's the difference, if any? This actually looks a little more familiar to me coming from a Windows world.

There are some people who prefer to compile things from source. It's usually tailored a little better to your system and runs a little quicker because the problem with package formats is that they can sometimes introduce some bloat into the system (rpm is well known for this). There's even a distribution called Gentoo which you have to compile completely from source.

[devils casper]

Th web site below seems to be explaining how to manually install ffmpeg.

Yum works only if your machine has internet access. It fetches packages from sources/repositories.
If there is no internet access, one has to manually install packages manually.