The NetBSD port for i386, amd64, mac68k, macppc, and many others can execute a great number of native Linux programs, using the Linux emulation layer. Generally, when you think about emulation you imagine something slow and inefficient because, often, emulations must reproduce hardware instructions and even architectures (usually from old machines) in software. In the case of the Linux emulation, this is radically different: it is only a thin software layer, mostly for system calls which are already very similar between the two systems. The application code itself is processed at the full speed of your CPU, so you don't get a degraded performance with the Linux emulation and the feeling is exactly the same as for native NetBSD applications.
This chapter explains how to configure the Linux emulation with an example: the installation of the well known Acrobat Reader version 7 program.
The installation of the Linux emulation is described in the compat_linux(8) man page; using the package system, only two steps are needed.
- Configuring the kernel.
- Installing the Linux libraries.
- Installing Linux applications like Acrobat Reader
If you use a GENERIC kernel you don't need to do anything because Linux compatibility is already enabled.
If you use a customized kernel, check that the following options are enabled:
option COMPAT_LINUX option EXEC_ELF32
or the following options if you are going to use 64-bit ELF binaries:
option COMPAT_LINUX option EXEC_ELF64
When you have compiled a kernel with the previous options, you can start installing the necessary software.
Usually, applications are linked against shared libraries, and for Linux applications, Linux shared libraries are needed. You can get the shared libraries from any Linux distribution, provided it's not too old, but the suggested method is to use the package system and install the libraries automatically (which uses SUSE libraries). When you install the libraries, the following happens:
A secondary root directory is created which will be used for Linux programs. This directory is
/emul/linux. The Linux programs in emulation mode will use this directory as their root directory and use files there. If a required file is not found, it will be searched with
/as root directory.
For example, if a Linux application opens
/etc/ld.so.conf, it will first be searched in
/emul/linux/etc/ld.so.conf, and if not found there, in
The shared libraries for Linux are installed. Most applications are linked dynamically and expect to find the necessary libraries on the system. For example, for Acrobat Reader, if you go to the
/usr/pkgsrc/print/acroread7and give the
make dependscommand, pkgsrc will fetch and install all dependencies for Acrobat Reader.
Both operations will be handled automatically by the package system, without the need of manual intervention from the user (we suppose that, by now, you have already begun to love the package system...). Note that this section describes manual installation of the Linux libraries.
To install the libraries, a program must be installed that handles the RPM
format: it is
rpm, which will be used to extract the SUSE libraries. Execute
make install in the
/usr/pkgsrc/misc/rpm/ directory to build
suse121_base package must be installed. The SUSE RPM files can be
downloaded by the package system or, if you have a SUSE CD, you can copy them in
/usr/pkgsrc/distfiles/suse121 directory and then run
make install after going to the
With the same method install
suse121_x11. The final
# pkg_info -a | grep suse suse_base-12.1nb3 Linux compatibility package suse_compat-12.1 Linux compatibility package with old shared libraries suse_x11-12.1 Linux compatibility package for X11
Note: Of course you can also install the packages binary. To do this, you
would either set the proper
PKG_PATH and then
# pkg_add rpm # pkg_add suse_base # pkg_add suse_compat # pkg_add suse_x11
# pkgin install rpm suse_base suse_compat suse_x11
Note: You can also skip this step when you are installing a package from
pkgsrc which requires Linux emulation! A good example for this is the package
www/opera, which will automatically install the packages needed for emulating
the Linux version of the Opera browser.
Now everything is ready for the installation of the Acrobat Reader program (or
other Linux programs). Change to
/usr/pkgsrc/print/acroread7 and give the
# make # make install
To download and install Acrobat Reader you need to add the line
/etc/mk.conf to accept the
Acrobat Reader license, simply follow the instructions given after
If we examine the outcome of the installation of the Linux libraries and
programs we find that
/emul/linux is a symbolic link pointing to
/usr/pkg/emul/linux, where the following directories have been created:
Note: Please always refer to
/emul/linux and not to
The latter is an implementation detail and may change in the future.
How much space is required for the Linux emulation software? On one system we got the following figure:
# cd /usr/pkg/emul # du -k /emul/linux/ ... 127804 /emul/linux/
Acrobat Reader, the program, has been installed in the usual directory for
/usr/pkg/bin. It can be run just as any other program:
$ acroread netbsd.pdf
Some Linux programs rely on a Linux-like
/proc filesystem. The NetBSD procfs
filesystem can emulate a
/proc filesystem that contains Linux-specific
pseudo-files. To accomplish this you can mount the procfs with the
# mount_procfs -o linux procfs /emul/linux/proc
In this example a Linux-like proc filesystem will be mounted to the
/emul/linux/proc directory. You can also let NetBSD mount it automatically
during the booting process of NetBSD, by adding the following line to
procfs /emul/linux/proc procfs ro,linux
Linux plugins for Mozilla-based browsers can be used on native NetBSD Firefox builds through nspluginwrapper, a wrapper that translates between the native browser and a foreign plugin. At the moment, nspluginwrapper only works reliably on Mozilla-based browsers that link against GTK2+ (GTK1+ is not supported). nspluginwrapper can be installed through pkgsrc:
# cd /usr/pkgsrc/www/nspluginwrapper # make install
Plugins can then be installed in two steps: first, the plugin has to be
installed on the system (e.g. through pkgsrc). After that the plugin should be
registered with the
nspluginwrapper by the users who want to use that
In this short example we will have a look at installing the Macromedia Flash plugin. We can fullfill the first step by installing the Flash plugin through pkgsrc:
# cd /usr/pkgsrc/multimedia/ns-flash # make install
After that an unprivileged user can register the Flash plugin:
$ nspluginwrapper -i /usr/pkg/lib/netscape/plugins/libflashplayer.so
The plugin should then be registered correctly. You can check this by using the
-l option of
nspluginwrapper -l). If the plugin is
listed, you can restart Firefox, and verify that the plugin was installed by
about:plugins in the location bar.
The following articles may be of interest for further understanding Linux (and other) emulation:
- Implementing Linux emulation on NetBSD. Peter Seebach. May 2004.
- Linux compatibility on BSD for the PPC platform, part 1. Emmanuel Dreyfus. May 2001.
- Linux compatibility on BSD for the PPC platform, part 2. Emmanuel Dreyfus. May 2001.
- Linux compatibility on BSD for the PPC platform, part 3. Emmanuel Dreyfus. Jun 2001.
- Linux compatibility on BSD for the PPC platform, part 4. Emmanuel Dreyfus. Jun 2001.
- Linux compatibility on BSD for the PPC platform, part 5. Emmanuel Dreyfus. Aug 2002.
- Irix binary compatibility, part 1. Emmanuel Dreyfus. Aug 2002.
- Irix binary compatibility, part 2. Emmanuel Dreyfus. Aug 2002.
- Irix binary compatibility, part 3. Emmanuel Dreyfus. Sep 2002.
- Irix binary compatibility, part 4. Emmanuel Dreyfus. Oct 2002.
- Irix binary compatibility, part 5. Emmanuel Dreyfus. Dec 2002.
- Irix binary compatibility, part 6. Emmanuel Dreyfus. Apr 2003.