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Dd September 26, 2021
Dt COMPAT_LINUX 8
Os
Sh NAME
Nm compat_linux
Nd setup procedure for running Linux binaries
Sh DESCRIPTION
Nx
supports running Linux binaries.
This applies to aarch64, alpha, amd64, arm, i386, m68k, and powerpc systems for now.
Both the a.out and ELF binary formats are supported.
Most programs should work.
Nx
aarch64 and amd64 can execute both 32-bit and 64-bit Linux programs.
Programs that will not work include some that use
i386-specific calls, such as enabling virtual 8086 mode.
Currently, sound is supported through OSSv3 compat.
Pp
The Linux compatibility feature is active
for kernels compiled with the
Dv COMPAT_LINUX
option enabled.
If support for Linux a.out executables is desired, the
Dv EXEC_AOUT
option should be enabled in addition to option
Dv COMPAT_LINUX .
Similarly, if support for Linux 32-bit and/or 64-bit ELF executables
is desired, the
Dv EXEC_ELF32
and/or
Dv EXEC_ELF64
options (respectively) should be enabled in addition to
Dv COMPAT_LINUX .
If sound support is desired,
Dv COMPAT_OSSAUDIO
should be enabled.
Pp
A lot of programs are dynamically linked.
This means that you will also need the Linux shared libraries that the
program depends on, and the runtime linker.
Also, you will need to create a
Dq shadow root
directory for Linux binaries on your
Nx
system.
This directory is named
Pa /emul/linux
or
Pa /emul/linux32
for 32-bit emulation on 64-bit systems.
Any file operations done by Linux programs run under
Nx
will look in this directory first.
So, if a Linux program opens, for example,
Pa /etc/passwd ,
Nx
will
first try to open
Pa /emul/linux/etc/passwd ,
and if that does not exist open the
Sq real
Pa /etc/passwd
file.
It is recommended that you install
Linux packages that include configuration files, etc under
Pa /emul/linux ,
to avoid naming conflicts with possible
Nx
counterparts.
Shared libraries should also be installed in the shadow tree.
Filenames that start "/../" are only looked up in the real root.
Pp
Generally, you will need to look for the shared libraries that Linux
binaries depend on only the first few times that you install a Linux
program on your
Nx
system.
After a while, you will have a sufficient
set of Linux shared libraries on your system to be able to run newly
imported Linux binaries without any extra work.
Ss Setting up shared libraries
Find the dependencies of a Linux binary using
Xr readelf 1 :
Bd -literal
$ readelf -d ./runner | grep Shared
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]
Ed
Pp
For x86, you can simply install the openSUSE shared libraries using the
Pa pkgsrc/emulators/suse131_*
or
Pa pkgsrc/emulators/suse131_32_*
packages.
Pp
For example, an application which requires
Pa libcrypto.so.1.0.0 ,
Pa libXext.so.6 ,
and
Pa libGL.so.1
will require
Dv openssl ,
Dv x11 ,
and
Dv glx ,
in addition to the
Dv base
SUSE package.
Pp
Otherwise, you may have to obtain shared libraries from another Linux
system, and copy them to e.g.
Pa /emul/linux/lib64 .
Ss Setting up procfs
Some Linux binaries expect procfs to be mounted and that it
contains some Linux-specific extensions.
If it's not the case, they behave unexpectedly or even crash.
Pp
Mount procfs on
Nx
using following command:
Bl -tag -width 123 -offset indent
It $ mount_procfs procfs /emul/linux/proc
El
Pp
You can also set up your system so that procfs is mounted automatically
on system boot, by putting an entry like the one below to
Pa /etc/fstab .
Bl -tag -width 123 -offset indent
It procfs /emul/linux/proc procfs ro
El
Pp
Note:
Xr mount_procfs 8
defaults to Linux flavored procfs since
Nx 5.0 .
Ensure you do not mount procfs with
Ar nolinux .
Pp
See
Xr mount_procfs 8
for further information.
Ss Setting up other files
Newer version of Linux use
Pa /etc/nsswitch.conf
for network information, such as NIS and DNS.
You must create or get a valid copy of this file and put it in
Pa /emul/linux/etc .
Sh CAVEATS
Nm
is generally not enabled in
Dv GENERIC
kernels for security reasons,
but is available as a module.
It must be added to
Xr modules.conf 5
to be used.
It will not be loaded automatically.
Sh BUGS
The information about Linux distributions will become outdated.
Pp
Absolute pathnames pointed to by symbolic links are only looked up in the
shadow root when the symbolic link itself was found by an absolute
pathname inside the shadow root.
This is not consistent.
Pp
Linux executables cannot handle directory offset cookies > 32 bits.
Should such an offset occur, you will see the message
Dq linux_getdents: dir offset too large for emulated program .
Currently, this can only
happen on NFS mounted file systems, mounted from servers that return
offsets with information in the upper 32 bits.
These errors should rarely happen, but can be avoided by mounting this
file system with offset translation enabled.
See the
Fl X
option to
Xr mount_nfs 8 .
The
Fl 2
option to
Xr mount_nfs 8
will also have the desired effect, but is less preferable.

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