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The NetBSD port for amd64, i386, alpha, 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.
The installation of the Linux emulation is described in the compat_linux(8) man page; using the package system only two steps are needed.
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 to install the provided libraries from openSUSE.
All Linux binaries exist entirely within the separate root
directories inside /emul/linux and
/emul/linux32.
The kernel will always search these paths first when looking
for shared objects required by Linux programs.
A number of useful Linux shared object binaries is provided by
pkgsrc, for running both 64-bit and 32-bit applications. The absolute
minimum required to run dynamically linked Linux applications are
are provided by the suse131_base and
suse131_32_base packages (or, if using binary
packages suse_base-13 and
suse32_base-13). Many other libraries are also
provided as separate packages.
Some packages in pkgsrc are provided as Linux binaries and
will also install all the required SUSE dependencies when installed.
However, this is uncommon. One such package is
adoptopenjdk11-bin.
It is possible to examine which libraries are required by a Linux program with readelf(1):
$readelf -d ./runnerDynamic section at offset 0x3a2e94 contains 40 entries: Tag Type Name/Value 0x00000001 (NEEDED) Shared library: [libstdc++.so.6] 0x00000001 (NEEDED) Shared library: [libz.so.1] 0x00000001 (NEEDED) Shared library: [libXxf86vm.so.1] 0x00000001 (NEEDED) Shared library: [libGL.so.1] 0x00000001 (NEEDED) Shared library: [libopenal.so.1] 0x00000001 (NEEDED) Shared library: [libm.so.6] 0x00000001 (NEEDED) Shared library: [librt.so.1] 0x00000001 (NEEDED) Shared library: [libpthread.so.0] 0x00000001 (NEEDED) Shared library: [libdl.so.2] 0x00000001 (NEEDED) Shared library: [libcrypto.so.1.0.0] 0x00000001 (NEEDED) Shared library: [libXext.so.6] 0x00000001 (NEEDED) Shared library: [libX11.so.6] 0x00000001 (NEEDED) Shared library: [libXrandr.so.2] 0x00000001 (NEEDED) Shared library: [libGLU.so.1] 0x00000001 (NEEDED) Shared library: [libssl.so.1.0.0] 0x00000001 (NEEDED) Shared library: [libgcc_s.so.1] 0x00000001 (NEEDED) Shared library: [libc.so.6]
For example, an application which requires
libcrypto.so.1.0.0,
libXext.so.6, and
libGL.so.1
will require openssl,
x11, and glx,
in addition to the base SUSE package.
Once the correct libraries are installed, no special steps are required to run a Linux program - simply type the command (if you acquired it as a non-pkgsrc download, include the full path on the filesystem). The kernel will detect it is a Linux executable and run it in the correct translation mode.
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:
bin/
dev/
etc/
lib/
lib64/
proc/
sbin/
usr/
var/
Please always refer to /emul/linux and not
to /usr/pkg/emul/linux.
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/... 399658 /emul/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 plugin.
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
(nspluginwrapper -l). If the plugin is listed,
you can restart Firefox, and verify that the plugin was installed
by entering about:plugins in the location
bar.
The following articles may be of interest for further understanding Linux (and other) emulation:
[chap-linux-further-implementing-linux-emul-on-netbsd] Implementing Linux emulation on NetBSD . May 2004.