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.

8.1.5. --version: Display the Current RPM Version

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:

# rpm --version

RPM version 2.3

#

8.2. Using rpm2cpio

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:

1. Install the package.
2. Make a copy of the file(s) you need.
3. Erase the package.

An easier way would be to use rpm2cpio.

8.2.1. rpm2cpio: What Does It Do?

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!

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:

# 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

Note that this is only the first few lines of output.

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:

# rpm2cpio logrotate-1.0-1.i386.rpm > blah.cpio

# file blah.cpio

blah.cpio: ASCII cpio archive (SVR4 with CRC)

#

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:

# cat logrotate-1.0-1.i386.rpm | rpm2cpio > blah.cpio

#

8.2.2. A More Real-World Example: Listing the Files in a Package File

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:

# rpm2cpio logrotate-1.0-1.i386.rpm | cpio -t

usr/man/man8/logrotate.8

usr/sbin/logrotate

14 blocks

#

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.

8.2.3. Extracting One or More Files from a Package File

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:

# rpm2cpio logrotate-1.0-1.i386.rpm |cpio -ivd usr/man/man8/logrotate.8

usr/man/man8/logrotate.8

14 blocks

#

In this case, the cpio options -i, -v, and -d direct cpio to do the following:

1. Extract one or more files from an archive.
2. 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.)
3. Create any directories that precede the filename specified in the cpio command.

So where did the file end up? The last option (-d) to cpio provides a hint. Let's take a look:

# 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

. . .

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!

8.3. Source Package Files and How to Use Them

One day, you may run across a package file with a name similar to the following:

etcskel-1.0-3.src.rpm

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:

# file foo.bar

foo.bar: RPM v2 bin i386 eject-1.2-2

#

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.