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<TITLE>Maximum RPM (RPM):Miscellanea:EarthWeb Inc.-</TITLE>
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<!-- TITLE=Maximum RPM (RPM)//-->
<!-- AUTHOR=Edward Bailey//-->
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<A NAME="PAGENUM-105"><P>Page 105</P></A>
<P>This is just the first screen of RPM's help command. To see the rest, give the command a
try. Practically everything there is to know about RPM is present in the
--help output. It's a bit too concise to learn RPM from, but it's enough to refresh your memory when the syntax of
a particular option escapes you.
</P>
<H4><A NAME="ch08_ 7">
8.1.5. --version: Display the Current RPM Version
</A></H4>
<P>If you're not sure what version of RPM is presently
installed on your system, the easiest way to find out is to ask RPM itself using the
--version option:
</P>
<!-- CODE SNIP //-->
<PRE>
# rpm --version
RPM version 2.3
#
</PRE>
<!-- END CODE SNIP //-->
<H4><A NAME="ch08_ 8">
8.2. Using rpm2cpio
</A></H4>
<P>From time to time, you might find it necessary to extract one or more files from a package
file. One way to do this would be the following:
</P>
<OL>
<LI> Install the package.
<LI> Make a copy of the file(s) you need.
<LI> Erase the package.
</OL>
<P>
An easier way would be to use rpm2cpio.
</P>
<H4><A NAME="ch08_ 9">
8.2.1. rpm2cpio: What Does It Do?
</A></H4>
<P>As the name implies, rpm2cpio takes an RPM package file and converts it
to a cpio archive. Because it's written to be used primarily as a filter, there's not much to be specified.
rpm2cpio takes only one argument, and even that's optional!
</P>
<P>The optional argument is the name of the package file to be converted. If there is no
filename specified on the command line, rpm2cpio will simply read from standard input and
convert that to a cpio archive. Let's give it a try:
</P>
<!-- CODE //-->
<PRE>
# rpm2cpio logrotate-1.0-1.i386.rpm
0707020001a86a000081a4000000000000000000000001313118bb000002c200000008000
000030000000000000000000000190000e73eusr/man/man8/logrotate.8." logrotate
- log file rotator
.TH rpm 8 "28 November 1995" "Red Hat Software" "Red Hat Linux"
.SH NAME
</PRE>
<!-- END CODE //-->
<P>Note that this is only the first few lines of output.
</P>
<P>What on earth is all that stuff? Remember that
rpm2cpio is written as a filter. It writes the
cpio archive contained in the package file to standard output, which, if you've not redirected it
somehow, is your screen. Here's a more reasonable example:
</P>
<A NAME="PAGENUM-106"><P>Page 106</P></A>
<!-- CODE SNIP //-->
<PRE>
# rpm2cpio logrotate-1.0-1.i386.rpm > blah.cpio
# file blah.cpio
blah.cpio: ASCII cpio archive (SVR4 with CRC)
#
</PRE>
<!-- END CODE SNIP //-->
<P>Here we've directed rpm2cpio to convert the
logrotate package file. We've also redirected
rpm2cpio's output to a file called blah.cpio. Next, using the
file command, we find that the resulting file is indeed a bona fide
cpio archive file. The following command is entirely
equivalent to the previous one and shows rpm2cpio's capability to read the package file from its
standard input:
</P>
<!-- CODE SNIP //-->
<PRE>
# cat logrotate-1.0-1.i386.rpm | rpm2cpio > blah.cpio
#
</PRE>
<!-- END CODE SNIP //-->
<H4><A NAME="ch08_ 10">
8.2.2. A More Real-World Example: Listing the Files in a
Package File
</A></H4>
<P>While there's nothing wrong with using rpm2cpio to create a
cpio archive file, it takes a few more steps and uses a bit more disk space than is strictly necessary. A somewhat cleaner
approach would be to pipe rpm2cpio's output directly into
cpio:
</P>
<!-- CODE SNIP //-->
<PRE>
# rpm2cpio logrotate-1.0-1.i386.rpm | cpio -t
usr/man/man8/logrotate.8
usr/sbin/logrotate
14 blocks
#
</PRE>
<!-- END CODE SNIP //-->
<P>In this example, we used the -t option to direct
cpio to produce a table of contents of the archive created by
rpm2cpio. This can make it much easier to get the right filename and path when
you want to extract a file.
</P>
<H4><A NAME="ch08_ 11">
8.2.3. Extracting One or More Files from a Package File
</A></H4>
<P>Continuing the previous example, let's extract the man page from the
logrotate package. In the table of contents, we see that the full path is
usr/man/man8/logrotate.8. All we need to do is to use the filename and path as shown here:
</P>
<!-- CODE SNIP //-->
<PRE>
# rpm2cpio logrotate-1.0-1.i386.rpm |cpio -ivd usr/man/man8/logrotate.8
usr/man/man8/logrotate.8
14 blocks
#
</PRE>
<!-- END CODE SNIP //-->
<P>In this case, the cpio options -i, -v, and -d direct
cpio to do the following:
</P>
<OL>
<LI> Extract one or more files from an archive.
<LI> Display the names of any files processed, along with the size of the archive file, in
512-byte blocks. (Note that the size displayed by
cpio is the size of the cpio archive and not the package file.)
<LI> Create any directories that precede the filename specified in the
cpio command.
</OL>
<A NAME="PAGENUM-107"><P>Page 107</P></A>
<P>So where did the file end up? The last option
(-d) to cpio provides a hint. Let's take a look:
</P>
<!-- CODE //-->
<PRE>
# ls -al
total 5
-rw-rw-r-- 1 root root 3918 May 30 11:02 logrotate-1.0-1.i386.rpm
drwx------ 3 root root 1024 Jul 14 12:42 usr
# cd usr
# ls -al
total 1
drwx------ 3 root root 1024 Jul 14 12:42 man
# cd man
# ls -al
total 1
drwx------ 2 root root 1024 Jul 14 12:42 man8
# cd man8
# ls -al
total 1
-rw-r--r-- 1 root root 706 Jul 14 12:42 logrotate.8
# cat logrotate.8
.\" logrotate - log file rotator
.TH rpm 8 "28 November 1995" "Red Hat Software" "Red Hat Linux"
.SH NAME
logrotate \- log file rotator
.SH SYNOPSIS
\fBlogrotate\fP [configfiles]
.SH DESCRIPTION
\fBlogrotate\fP is a tool to prevent log files from growing without
. . .
</PRE>
<!-- END CODE //-->
<P>Since the current directory didn't have a
usr/man/man8/ path in it, the -d option caused
cpio to create all the directories leading up to the
logrotate.8 file in the current directory. Based
on this, it's probably safest to use cpio outside the normal system directories unless you're
comfortable with cpio and you know what you're doing!
</P>
<H4><A NAME="ch08_ 12">
8.3. Source Package Files and How to Use Them
</A></H4>
<P>One day, you may run across a package file with a name similar to the following:
</P>
<!-- CODE SNIP //-->
<PRE>
etcskel-1.0-3.src.rpm
</PRE>
<!-- END CODE SNIP //-->
<P>Notice the src. Is that a new kind of computer? If you use RPM on an Intel-based
computer, you'd normally expect to find i386 there. Maybe someone messed up the name of the file.
Well, we know that the file command can display information about a package file, even if
the filename has been changed. We've used it before to figure out what package a file contains:
</P>
<!-- CODE SNIP //-->
<PRE>
# file foo.bar
foo.bar: RPM v2 bin i386 eject-1.2-2
#
</PRE>
<!-- END CODE SNIP //-->
<P>In this example, foo.baris an RPM version 2 file.
bin indicates that the file contains an executable package, and
i386 means that the package was built for Intel processors. The
package is called eject version 1.2, release 2.
</P>
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