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<TITLE>Maximum RPM (RPM):An Introduction to Package Management:EarthWeb Inc.-</TITLE>

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<A NAME="PAGENUM-13"><P>Page 13</P></A>





<H4><A NAME="ch01_ 14">

1.4.1. RPM's Package Labels

</A></H4>



<P>Every package built for RPM has to have a specific set of information that uniquely identifies it. We call this information a package

label. Here are two sample package labels:

</P>



<UL>

<LI>          nls-1.0-1

<LI>          perl-5.001m-4

</UL>



<P>Although these labels look like they have very little in common, in fact they both follow

RPM's package labeling convention. There are three different components in every package label.

Let's look at each one in order.

</P>



<B>

1.4.1.1. Component 1: The Software's Name

</B>



<P>Every package label begins with the name of the software. The name might be derived

from the name of the application packaged, or it might be a name describing a group of related

programs bundled together by the package builder. The software names in the examples

shown previously are nls and perl. As you can see, the software name is separated from the rest of

the package label by a dash.

</P>



<B>

1.4.1.2. Component 2: The Software's Version

</B>



<P>Next in the package label is an identifier that describes the version of the software being

packaged. If the package builder bundled a number of related programs together, the software

version is probably a number of the package builder's choosing. However, if the package

consists of one major application, the software version normally comes directly from the

application's developer. The actual version specification is quite flexible, as can be seen in the examples.

The versions shown are 1.0 and 5.001m. A dash separates the software version from the

remainder of the package label.

</P>



<B>

1.4.1.3. Component 3: The Package's Release

</B>



<P>The package release is the most unambiguous part of a package label. It is a number chosen

by the package builder. It reflects the number of times the package has been rebuilt using the

same version of software. Normally, the rebuilds are due to bugs uncovered after the package

has been in use for a while. By tradition, the package release starts at 1. The package releases in

the example are 1 and 4.

</P>



<H4><A NAME="ch01_ 15">

1.4.2. Labels and Names: Similar but Distinct

</A></H4>



<P>Package labels are used internally by RPM. For example, if you ask RPM to list every

installed package, it will respond with a list of package labels. When a package file is created, part of

the filename consists of the package label. There is no technical requirement for this, but it

does make it easier to keep track of things.

</P>



<A NAME="PAGENUM-14"><P>Page 14</P></A>







<P>However, a package file may be renamed, and the new filename won't confuse RPM in

the least because the package label is contained within the file. For a fairly technical view of

the inside of a package file, see Appendix A.

</P>



<H4><A NAME="ch01_ 16">

1.4.3. Packagewide Information

</A></H4>



<P>Some of the information contained in a package is general in nature. This information includes such items as

</P>



<UL>

<LI>          The date and time the package was built

<LI>          A description of the package's

contents

<LI>         The total size of all the

files installed by the package

<LI>          Information that allows the package to be grouped with similar packages

<LI>          A digital

signature that can be used to verify the authenticity and integrity of

the package

</UL>

<BR>

<P>



<CENTER>

<TABLE BGCOLOR="#FFFF99">

<TR><TD><B>

NOTE

</B></TD></TR>

<TR><TD>

<BLOCKQUOTE>

For more information on RPM's signature checking capability, refer to

section 7.1 in Chapter 7, &quot;Using RPM to Verify Package Files.&quot;

</BLOCKQUOTE></TD></TR>

</TABLE></CENTER>

</P>

<H4><A NAME="ch01_ 17">

1.4.4. Per-File Information

</A></H4>



<P>Each package also contains information about every file contained in the package. The

information includes

</P>



<UL>

<LI>          The name of every file and where it is to be installed

<LI>          Each file's permissions

<LI>          Each file's owner and group specifications

<LI>          The MD5 checksum of each file

</UL>



<BR>

<P>



<CENTER>

<TABLE BGCOLOR="#FFFF99">

<TR><TD><B>

NOTE

</B></TD></TR>

<TR><TD>

<BLOCKQUOTE>

We'll discuss MD5 checksums in greater detail in section 6.1 of Chapter

6, &quot;Using RPM to Verify Installed Packages.&quot;

</BLOCKQUOTE></TD></TR>

</TABLE></CENTER>

</P>

<UL>

<LI>          The file's contents

</UL>



<A NAME="PAGENUM-15"><P>Page 15</P></A>







<H3><A NAME="ch01_ 18">

1.5. Summary

</A></H3>



<P>So a package management system uses the computer to keep track of all the various bits

and pieces that comprise an application or an entire operating system. Most package

management systems use a specially formatted file to keep everything together in a single, easily

manageable entity, or package. Additionally, package management systems tend to provide one or more

of the following functions:

</P>



<UL>

<LI>          Installing new packages

<LI>          Removing old packages

<LI>          Upgrading from an old package to a new one

<LI>          Obtaining information about installed packages

</UL>



<P>RPM has been designed with Red Hat Software's past package management experiences in

mind. PM and RPP provided most of these functions with varying degrees of success. Ewing and

Troan have worked hard to make RPM better than its predecessors in every way. Now it's time to

see how they did it and learn how to use RPM!

</P>



<A NAME="PAGENUM-16"><P>Page 16</P></A>

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