path: root/share/man/man8/compat_linux.8

.\"	$OpenBSD: compat_linux.8,v 1.22 2002/05/09 06:09:05 jasoni Exp $
.\"	$NetBSD: compat_linux.8,v 1.2 1995/10/16 20:17:59 fvdl Exp $
.\"
.\" Copyright (c) 1995 Frank van der Linden
.\" All rights reserved.
.\"
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.\" modification, are permitted provided that the following conditions
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.\"    must display the following acknowledgement:
.\"      This product includes software developed for the NetBSD Project
.\"      by Frank van der Linden
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.Dd March 2, 1995
.Dt compat_linux 8
.Os
.Sh NAME
.Nm compat_linux
.Nd setup procedure for running Linux binaries under emulation
.Sh DESCRIPTION
.Ox
supports running Linux binaries.
This only applies to i386 systems for now.
Both the a.out and ELF binary formats are supported.
Most programs should work, including the ones that use the Linux SVGAlib.
Additionally, OSS audio is emulated, so Linux bins can access the native audio
transparently.
Programs that will not work include those that use the Linux /proc filesystem
(which is different from the optional 
.Ox
/proc
filesystem), and i386-specific calls, such as enabling virtual 8086 mode.
.Pp
The Linux compatibility feature is active
for kernels compiled with the
.Nm COMPAT_LINUX
option 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 "shadow root" directory for Linux binaries
on your
.Ox
system.
This directory is named /emul/linux.
Any file operations done by Linux programs run under
.Ox
will look in this directory first.
So, if a Linux program opens, for example, /etc/passwd,
.Ox
will first try to open /emul/linux/etc/passwd, and if that does not exist
open the 'real' /etc/passwd file.
It is recommended that you install Linux packages that include configuration
files, etc under /emul/linux, to avoid naming conflicts with possible
.Ox
counterparts.
Shared libraries should also be installed in the shadow tree.
.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
.Ox
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
How to get to know which shared libraries Linux binaries need, and where
to get them?
Basically, there are 3 possibilities (when following these instructions:
you will need to be root on your
.Ox
system to do the necessary installation steps).
.Pp
.Bl -tag -width 123 -compact
.It 1.
You have access to the
.Ox
.Xr ports 7
system.
Install the port named
.Nm redhat_base
in the
.Nm emulators
category.
The
.Nm redhat_base
port contains the shared libraries, binaries, and other related files
necessary to run Linux applications.
Access to a Linux system is not needed.
.Pp
.It 2.
You have access to a Linux system.
In this case you can temporarily install the binary there, see what
shared libraries it needs, and copy them to your
.Ox
system.
Example: you have just ftp-ed the Linux binary of Doom.
Put it on the Linux system you have access to, and check which shared
libraries it needs by running `ldd linuxxdoom':
.Pp
.Bl -tag -width 123 -compact -offset indent
.It (me@linux) ldd linuxxdoom
.nf
libXt.so.3 (DLL Jump 3.1) => /usr/X11/lib/libXt.so.3.1.0
libX11.so.3 (DLL Jump 3.1) => /usr/X11/lib/libX11.so.3.1.0
libc.so.4 (DLL Jump 4.5pl26) => /lib/libc.so.4.6.29
.fi
.El
.Pp
You would need go get all the files from the last column, and
put them under /emul/linux, with the names in the first column
as symbolic links pointing to them.
This means you eventually have these files on your
.Ox
system:
.Pp
.nf
/emul/linux/usr/X11/lib/libXt.so.3.1.0
/emul/linux/usr/X11/lib/libXt.so.3 (symbolic link to the above)
/emul/linux/usr/X11/lib/libX11.so.3.1.0
/emul/linux/usr/X11/lib/libX11.so.3 (symbolic link to the above)
/emul/linux/lib/libc.so.4.6.29
/emul/linux/lib/libc.so.4 (symbolic link to the above)
.fi
.Pp
Note that if you already have a Linux shared library with a
matching major revision number to the first column of the 'ldd'
output, you won't need to copy the file named in the last column
to your system, the one you already have should work.
It is advisable to copy the shared library anyway if it is a newer version,
though.
You can remove the old one, as long as you make the symbolic
link point to the new one.
So, if you have these libraries on your system:
.Pp
.nf
/emul/linux/lib/libc.so.4.6.27
/emul/linux/lib/libc.so.4 -> /emul/linux/lib/libc.so.4.6.27
.fi
.Pp
and you find that the ldd output for a new binary you want to
install is:
.nf
.Pp
libc.so.4 (DLL Jump 4.5pl26) => /lib/libc.so.4.6.29
.fi
.Pp
you won't need to worry about copying /lib/libc.so.4.6.29 too,
because the program should work fine with the slightly older version.
You can decide to replace the libc.so anyway, and that should leave
you with:
.Pp
.nf
/emul/linux/lib/libc.so.4.6.29
/emul/linux/lib/libc.so.4 -> /emul/linux/lib/libc.so.4.6.29
.fi
.Pp
Please note that the symbolic link mechanism is
.Nm only
needed for Linux binaries, the
.Ox
runtime linker takes care of looking for matching major revision numbers
itself, you don't need to worry about that.
.Pp
Finally, you must make sure that you have the Linux runtime linker
and its config files on your system.
You should copy these files from the Linux system to their appropriate
place on your
.Ox
system (in the /emul/linux tree):
.Pp
.nf
/lib/ld.so
/etc/ld.so.cache
/etc/ld.so.config
.fi
.Pp
.It 3.
You don't have access to a Linux system.
In that case, you should get the extra files you need from various
ftp sites.
Information on where to look for the various files is appended
below.
For now, let's assume you know where to get the files.
.Pp
Retrieve the following files (from _one_ ftp site to avoid
any version mismatches), and install them under /emul/linux
(i.e. /foo/bar is installed as /emul/linux/foo/bar):
.Pp
.nf
/sbin/ldconfig
/usr/bin/ldd
/lib/libc.so.x.y.z
/lib/ld.so
.fi
.Pp
ldconfig and ldd don't necessarily need to be under /emul/linux,
you can install them elsewhere in the system too.
Just make sure they don't conflict with their
.Ox
counterparts.
A good idea would be to install them in /usr/local/bin as ldconfig-linux
and ldd-linux.
.Pp
Create the file /emul/linux/etc/ld.so.conf, containing the
directories in which the Linux runtime linker should look
for shared libs.
It is a plain text file, containing a directory
name on each line.
/lib and /usr/lib are standard, you could add the following:
.Pp
.nf
/usr/X11/lib
/usr/local/lib
.fi
.Pp
Note that these are mapped to /emul/linux/XXXX by OpenBSD's compat
code, and should exist as such on your system.
.Pp
Run the Linux ldconfig program.
It should be statically linked, so it doesn't need any shared libraries
by itself.
It will create the file /emul/linux/etc/ld.so.cache
You should rerun the Linux version of the ldconfig program
each time you add a new shared library.
.Pp
You should now be set up for Linux binaries which only need
a shared libc.
You can test this by running the Linux ldd on itself.
Suppose that you have it installed as ldd-linux, it should produce
something like:
.Pp
.Bl -tag -width 123 -compact -offset indent
.It % ldd-linux `which ldd-linux`
libc.so.4 (DLL Jump 4.5pl26) => /lib/libc.so.4.6.29
.El
.Pp
This been done, you are ready to install new Linux binaries.
Whenever you install a new Linux program, you should check
if it needs shared libraries, and if so, whether you have
them installed in the /emul/linux tree.
To do this, you run the Linux version ldd on the new program, and
watch its output.
ldd (see also the manual page for ldd(1)) will print a list
of shared libraries that the program depends on, in the
form  <majorname> (<jumpversion>) => <fullname>.
.Pp
If it prints "not found" instead of <fullname> it means that
you need an extra library.
Which library this is, is shown
in <majorname>, which will be of the form libXXXX.so.<N>
You will need to find a libXXXX.so.<N>.<mm> on a Linux ftp site,
and install it on your system.
The XXXX (name) and <N> (major revision number) should match;
the minor number(s) <mm> are less important, though it is
advised to take the most recent version.
.El
.Ss Finding the necessary files.
.Nm Note:
the information below is valid as of the time this
document was written (March, 1995), but certain details
such as names of ftp sites, directories and distribution names
may have changed by the time you read this.
You can also save yourself a lot of headaches by using the
.Ox
.Xr ports 7
system (possibility 3, above).
.Pp
Linux is distributed by several groups that make their own set
of binaries that they distribute.
Each distribution has its own name, like "Slackware" or "Yggdrasil".
The distributions are available on a lot of ftp sites.
Sometimes the files are unpacked, and you can get the individual
files you need, but mostly they are stored in distribution sets,
usually consisting of subdirectories with gzipped tar files in them.
The primary ftp sites for the distributions are:
.Pp
.nf
sunsite.unc.edu:/pub/Linux/distributions
tsx-11.mit.edu:/pub/linux/distributions
.fi
.Pp
Some European mirrors:
.Pp
.nf
ftp.luth.se:/pub/linux/distributions
ftp.demon.co.uk:/pub/linux/distributions
src.doc.ic.ac.uk:/packages/linux/distributions
.fi
.Pp
For simplicity, let's concentrate on Slackware here.
This distribution consists of a number of subdirectories, containing
separate packages.
Normally, they're controlled by an install program, but you can
retrieve files "by hand" too.
First of all, you will need to look in the "contents" subdir of
the distribution.
You will find a lot of small textfiles here describing the contents of
the separate packages.
The fastest way to look something up is to retrieve all
the files in the contents subdirectory, and grep through them for the file
you need.
Here is an example of a list of files that you might need, and
in which contents-file you will find it by grepping through them:
.Bd -unfilled -offset indent
Needed                  Package

ld.so                   ldso
ldconfig                ldso
ldd                     ldso
libc.so.4               shlibs
libX11.so.6.0           xf_lib
libXt.so.6.0            xf_lib
libX11.so.3             oldlibs
libXt.so.3              oldlibs
.Ed
.Pp
So, in this case, you will need the packages ldso, shlibs, xf_lib and oldlibs.
In each of the contents-files for these packages, look for a line saying
"PACKAGE LOCATION", it will tell you on which 'disk' the package is,
in our case it will tell us in which subdirectory we need to look.
For our example, we would find the following locations:
.Bd -unfilled -offset indent
Package                 Location

ldso                    diska2
shlibs                  diska2
oldlibs                 diskx6
xf_lib                  diskx9
.Ed
.Pp
The locations called "diskXX" refer to the "slakware/XX" subdirectories
of the distribution, others may be found in the "contrib" subdirectory.
In this case, we could now retrieve the packages we need by retrieving
the following files (relative to the root of the Slackware distribution
tree):
.Pp
.nf
slakware/a2/ldso.tgz
slakware/a2/shlibs.tgz
slakware/x6/oldlibs/tgz
slakware/x9/xf_lib.tgz
.fi
.Pp
Extract the files from these gzipped tarfiles in your /emul/linux directory
(possibly omitting or afterwards removing files you don't need), and you
are done.
.Ss Programs using SVGAlib
SVGAlib binaries require some extra care.
The pcvt virtual console driver has to be in the kernel for them to work,
and you will also have to create some symbolic links in the /emul/linux/dev
directory, namely:
.Pp
.nf
/emul/linux/dev/console -> /dev/tty
/emul/linux/dev/mouse -> whatever device your mouse is connected to
/emul/linux/dev/ttyS0 -> /dev/tty00
/emul/linux/dev/ttyS1 -> /dev/tty01
.fi
.Pp
Be warned: the first link mentioned here makes SVGAlib binaries
work, but may confuse others, so you may have to remove it again at
some point.
.Ss Programs using OSS (Linux) audio
Only the DSP device is emulated, the following link should be created:
.Pp
.nf
/emul/linux/dev/dsp -> /dev/audio
.fi
.Ss Other links Linux bins may require
CD-ROM support requires a link to your cdrom device, similar to:
.Pp
.nf
/emul/linux/dev/cdrom -> /dev/cd0a   (first scsi cdrom)
.fi
.Ss File systems
Many Linux binaries expect /proc to have procfs mounted on it.
Some binaries will require it to be mounted using the
.Fl o Ar linux
option.
.Sh BUGS
The information about Linux distributions may become outdated.
.Pp
Linux ELF binaries may be detected as svr4 binaries. 
This can usually be fixed with
.Xr elf2olf 1
by setting the OLF opsys tag to Linux (eg: elf2olf -o linux <linux_binary>).
.Pp
.Nm
is currently only supported on the i386.