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 to:
An easier way would be to use rpm2cpio.
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 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
- log fi
.TH rpm 8 "28 November 1995" "Red Hat Software" "Red Hat Linux"
(We've just shown the first few lines of output.)
What on earth is all that stuff? Remember, 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 true-blue cpio archive file. The following command is entirely equivalent to the one above and shows rpm2cpio's ability to read the package file from its standard input:
# cat logrotate-1.0-1.i386.rpm | rpm2cpio > blah.cpio
While there's nothing wrong with using rpm2cpio to actually create a cpio archive file, it's 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
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.
Continuing the example above, 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 below:
# rpm2cpio logrotate-1.0-1.i386.rpm |cpio -ivd usr/man/man8/logrotate.8
In this case, the cpio options -i, -v, and -d direct cpio to:
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!