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4. Compatibility issues

4.1 How compatible is Debian with other distributions of Linux?

Debian developers communicate with other Linux distribution creators in an effort to maintain binary compatibility across Linux distributions. Most commercial Linux products run as well under Debian as they do on the system upon which they were built.

Debian GNU/Linux adheres strictly to the Linux File System Structure (now known as the FHS). However, there is room for interpretation in some of the rules within this standard, so there may be differences between a Debian system and other Linux systems.

4.2 How source code compatible is Debian with other Unix systems?

For most applications Linux source code is compatible with other Unix systems. It supports almost everything that is available in System V Unix systems and the free and commercial BSD- derived systems. However in the Unix business such claim has nearly no value because there is no way to prove it. In the software development area complete compatibility is required instead of compatibility in "about most" cases. So years ago the need for standards arose, and nowadays POSIX.1 (IEEE Standard 1003.1-1990) is one of the major standards for source code compatibility in Unix-like operating systems.

Linux is intended to adhere to POSIX.1, but the POSIX standards cost real money and the POSIX.1 (and FIPS 151-2) certification is quite expensive; this made it more difficult for the Linux developers to work on complete POSIX conformance. The certification costs make it unlikely that Debian will get an official conformance certification even if it completely passed the validation suite. (The validation suite is now freely available, so it is expected that more people will work on POSIX.1 issues.)

Unifix GmbH (Braunschweig, Germany) developed a Linux system that has been certified to conform to FIPS 151-2 (a superset of POSIX.1). This technology is available in Unifix' own distribution called Unifix Linux 2.0 and in Lasermoon's *Linux-FT. Currently Unifix merges its patches into the Linux kernel, gcc and other tools; so it is expected that their fixes towards POSIX.1 conformance will be available in Debian (and other distributions).

4.3 Can I use Debian packages (".deb" files) on my RedHat/Slackware/... Linux system?Can I use RedHat packages (".rpm" files) on my Debian GNU/Linux system?

Different Linux distributions use different package formats and different package management programs.

You probably can:

A program to unpack a Debian package onto a Linux host that is been built from a `foreign' distribution is available, and will generally work, in the sense that files will be unpacked. The converse is probably also true, that is, a program to unpack a RedHat or Slackware package on a host that is based on Debian Linux will probably succeed in unpacking the package and placing most files in their intended directories. This is largely a consequence of the existence (and broad adherence to) the Linux File System Standard.

You probably do not want to:

Most package managers write administrative files when they are used to unpack an archive. These administrative files are generally not standardized. Therefore, the effect of unpacking a Debian package on a `foreign' host will have unpredictable (certainly not useful) effects on the package manager on that system. Likewise, utilities from other distributions might succeed in unpacking their archives on Debian systems, but will probably cause the Debian package management system to fail when the time comes to upgrade or remove some packages, or even simply to report exactly what packages are present on a system.

A better way:

The Linux File System Standard (and therefore Debian GNU/Linux) requires that subdirectories under /usr/local/ be entirely under the user's discretion. Therefore, users can unpack `foreign' packages into this directory, and then manage their configuration, upgrade and removal individually.

4.4 Is Debian able to run my old "a.out" programs?

To execute a program whose binary is in a.out (i.e., QMAGIC or ZMAGIC) format,

If you have a commercial application in a.out format, now would be a good time to ask them to send you an ELF upgrade.

4.5 Can Debian be used to compile "a.out" programs?

To compile programs in the a.out binary format,

4.6 How should I install a non-Debian package?

Files under the directory /usr/local/ are not under the control of the Debian package management system. Therefore, it is good practice to place the source code for your program in /usr/local/src/. For example, you might extract the files for a package named "foo.tar" into the directory /usr/local/src/foo. After you compile them, place the binaries in /usr/local/bin/, the libraries in /usr/local/lib/, and the configuration files in /usr/local/etc/.

If your programs and/or files really must be placed in some other directory, you could still store them in /usr/local/, and build the appropriate symbolic links from the required location to its location in /usr/local/, e.g., you could make the link

ln -s /usr/local/bin/foo /usr/bin/foo

In any case, if you obtain a package whose copyright allows redistribution, you should consider making a Debian package of it, and uploading it for the Debian system. Guidelines for becoming a package developer are included in the Debian policy manual.

4.7 Why can't I compile programs that require libtermcap?

Debian uses the terminfo database and the ncurses library of terminal interface routes, rather than the termcap database and the termcap library. Users who are compiling programs that require some knowledge of the terminal interface should replace references to libtermcap with references to libncurses.

To support binaries that have already been linked with the termcap library, and for which you do not have the source, Debian provides a package called termcap-compat. This provides both and /etc/termcap. Install this package if the program fails to run with the error message "can't load library ''", or complains about a missing /etc/termcap file.

4.8 Why can't I install AccelX?

AccelX uses the termcap library for installation. See about termcap above.

4.9 Why do I get "Can't find" errors when I try to run foo?

This error message could mean that the program is in a.out format. In this case you need to install the xcompat package.

4.10 Can I install and compile a kernel without some Debian-specific tweaking?

Yes. But you have to understand the Debian policy with respect to headers.

The Debian C libraries are built with the most recent stable releases of the gcc headers. For example, the Debian-1.2 release used version 5.4.13 of the headers. This practice contrasts with the Linux kernel source packages distributed at all Linux FTP archive sites, which uses even more recent versions of the headers. The kernel headers distributed with the kernel source are located in /usr/include/linux/include/.

If you need to compile a program with kernel headers that are newer than those provided by libc5-dev, then you must add -I/usr/src/linux/include/ to your command line when compiling. This came up at one point, for example, with the packaging of the automounter daemon (amd). When new kernels changed some internals dealing with NFS, amd needed to know about them. This required the inclusion of the latest kernel headers.

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