language and designed to be lightweight and cross-platform.
.
This browser is based on the Firefox source-code, with minor
modifications. Historically, this browser was previously known as
Firebird and Phoenix.
GOING FURTHER Comparison of versions
Since dpkg is the program for handling Debian packages, it also provides the reference implementation of the logic of comparing version numbers. This is why it has a --compare-versions option, usable by external programs (especially configuration scripts executed by dpkg itself). This option requires three parameters: a version number, a comparison operator, and a second version number. The different possible operators are lt (strictly less than), le (less than or equal to), eq (equal), ne (not equal), ge (greater than or equal to), and gt (strictly greater than). If the comparison is correct, dpkg gives the return code, 0 (success); if not, it gives a non-zero return value (indicating failure).
$ dpkg --compare-versions 1.2-3 gt 1.1-4
$ echo $?
0
$ dpkg --compare-versions 1.2-3 lt 1.1-4
$ echo $?
1
$ dpkg --compare-versions 2.6.0pre3-1 lt 2.6.0-1
$ echo $?
1
Note the unexpected failure of the last comparison: for dpkg, pre, usually denoting a pre-release, has no particular meaning, and this program compares the alphabetic characters in the same way as the numbers (a <b <c ...), in alphabetical order. This is why it considers “0pre3” to be greater than “0”. When we want a package's version number to indicate that it is a pre-release, we use the tilde character, “~”:
$ dpkg --compare-versions 2.6.0~pre3-1 lt 2.6.0-1
$ echo $?
0
5.4.4. dpkg's Log File
A recently introduced feature in dpkg is that it keeps a log of all of its actions in /var/log/dpkg.log. This log is extremely verbose, since it details every one of the stages through which packages handled by dpkg go. In addition to offering a way to track dpkg's behavior, it helps, above all, to keep a history of the development of the system: one can find the exact moment when each package has been installed or updated, and this information can be extremely useful in understanding a recent change in behavior. Additionally, all versions being recorded, it is easy to cross-check the information with the changelog.Debian.gz for packages in question, or even with online bug reports.
5.5. Coexistence with Other Packaging Systems
Debian packages are not the only software packages used in the free software world. The main competitor is the RPM format for Red Hat Linux and its many derivatives. Red Hat is a very popular, commercial distribution. It is common for software provided by third parties to be offered as RPM packages rather than Debian.
In this case, you should know that the program rpm, which handles RPM packages, is available as a Debian package, so it is possible to use this package format on Debian. Care should be taken, however, to limit these manipulations to extract the information from a package or to verify its integrity. It is, in truth, unreasonable to use rpm to install an RPM on a Debian system; RPM uses its own database, separate from those of native software (such as dpkg). This is why it is not possible to ensure a stable coexistence of two packaging systems.
On the other hand, the alien utility can convert RPM packages into Debian packages, and vice versa.
COMMUNITY Encouraging the adoption of .deb
If you regularly use the alien program to install RPM packages coming from one of your providers, do not hesitate to write to them and amicably express your strong preference for the .deb format. Note that the format of the package is not everything: a .deb package built with alien or prepared for a version of Debian different than that which you use, even for a derivative distribution like Ubuntu, would probably not offer the same level of quality and integration as a package specifically developed for Debian Squeeze.
$ fakeroot alien --to-deb phpMyAdmin-2.0.5-2.noarch.rpm
phpmyadmin_2.0.5-2_all.deb generated
$ ls -s phpmyadmin_2.0.5-2_all.deb
64 phpmyadmin_2.0.5-2_all.deb
You will find that this process is extremely simple. You must know, however, that the package generated does not have any information on dependencies, since the dependencies in the two packaging formats don't have systematic correspondance. The administrator, thus, must manually ensure that the converted package will function correctly, and this is why Debian packages thus generated should be avoided as much as possible. Fortunately, Debian has the largest collection of software packages of all distributions, and it is likely that whatever you seek is already in there.
Looking at the man page for the alien command, you will also note that this program also handles other packaging formats, especially those from the Slackware distribution (they are a simple tar.gz archive).
The stability of the software deployed using the dpkg tool contributes to Debian's fame. The APT suite of tools, described in the following chapter, preserves this advantage, while relieving the administrator from managing the status of packages, a necessary but difficult task.
Chapter 6. Maintenance and Updates: The APT Tools
What makes Debian so popular with administrators is how easily software can be installed and how easily the whole system can be updated. This unique advantage is largely due to the APT program, the features of which Falcot Corp administrators studied with enthusiasm.
APT is the abbreviation for Advanced Package Tool. What makes this program “advanced” is its approach to packages. It doesn't simply evaluate them individually, but it considers them as a whole and produces the best possible combination of packages depending on what is available and compatible (according to dependencies).
VOCABULARY Package source and source package
The word source can be ambiguous. A source package — a package containing the source code of a program — should not be confused with a package source — a repository (website, FTP server, CD-ROM, local directory, etc.) which contains packages.
APT needs to be given a “list of package sources”: the file /etc/apt/sources.list will list the different repositories (or “sources”) that publish Debian packages. APT will then import the list of packages published by each of these sources. This operation is achieved by downloading Packages.gz or Packages.bz2 files (in case of a source of binary packages) and Sources.gz or Sources.bz2 files (in case of a source of source packages) and by analyzing their contents. When an old copy of these files is already present, APT can update it by only downloading the differences (see sidebar TIP Incremental upgrade).
BACK TO BASICS gzip, bzip2, LZMA and XZ Compression
A .gz extension refers to a file compressed with the gzip utility. gzip is the fast and efficient traditional Unix utility to compress files. Newer tools achieve better rates of compression but require more calculation time to compress a file. Among them, and by order of appearance, there are bzip2 (generating files with a .bz2 extension), lzma (generating .lzma files) and xz (generating .xz files).