COMPAT_FREEBSD(8) BSD System Manager's Manual COMPAT_FREEBSD(8)
compat_freebsd -- setup procedure for running FreeBSD binaries
NetBSD supports running FreeBSD binaries. Most binaries should work,
except programs that use FreeBSD-specific features. These include
i386-specific calls, such as syscons utilities. The FreeBSD compatibil-
ity feature is active for kernels compiled with the COMPAT_FREEBSD option
A lot of programs are dynamically linked. This means, that you will also
need the FreeBSD shared libraries that the program depends on, and the
runtime linker. Also, you will need to create a ``shadow root'' direc-
tory for FreeBSD binaries on your NetBSD system. This directory is named
/emul/freebsd. Any file operations done by FreeBSD programs run under
NetBSD will look in this directory first. So, if a FreeBSD program
opens, for example, /etc/passwd, NetBSD will first try to open
/emul/freebsd/etc/passwd, and if that does not exist open the 'real'
/etc/passwd file. It is recommended that you install FreeBSD packages
that include configuration files, etc under /emul/freebsd, to avoid nam-
ing conflicts with possible NetBSD counterparts. Shared libraries should
also be installed in the shadow tree.
Generally, you will need to look for the shared libraries that FreeBSD
binaries depend on only the first few times that you install a FreeBSD
program on your NetBSD system. After a while, you will have a sufficient
set of FreeBSD shared libraries on your system to be able to run newly
imported FreeBSD binaries without any extra work.
Setting up shared libraries
How to get to know which shared libraries FreeBSD binaries need, and
where to get them? Basically, there are 2 possibilities (when following
these instructions: you will need to be root on your NetBSD system to do
the necessary installation steps).
1. You have access to a FreeBSD system. In this case you can temporar-
ily install the binary there, see what shared libraries it needs,
and copy them to your NetBSD system. Example: you have just ftp-ed
the FreeBSD binary of SimCity. Put it on the FreeBSD system you
have access to, and check which shared libraries it needs by running
me@freebsd% ldd /usr/local/lib/SimCity/res/sim
-lXext.6 => /usr/X11R6/lib/libXext.so.6.0 (0x100c1000)
-lX11.6 => /usr/X11R6/lib/libX11.so.6.0 (0x100c9000)
-lc.2 => /usr/lib/libc.so.2.1 (0x10144000)
-lm.2 => /usr/lib/libm.so.2.0 (0x101a7000)
-lgcc.261 => /usr/lib/libgcc.so.261.0 (0x101bf000)
You would need go get all the files from the last column, and put
them under /emul/freebsd. This means you eventually have these
files on your NetBSD system:
Note that if you already have a FreeBSD shared library with a match-
ing 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. So, if you have these libraries on your system:
and you find that the ldd output for a new binary you want to
-lc.2 => /usr/lib/libc.so.2.1 (0x10144000)
You won't need to worry about copying /usr/lib/libc.so.2.1 too,
because the program should work fine with the slightly older ver-
sion. You can decide to replace the libc.so anyway, and that should
leave you with:
Finally, you must make sure that you have the FreeBSD runtime linker
and its config files on your system. You should copy these files
from the FreeBSD system to their appropriate place on your NetBSD
system (in the /emul/freebsd tree):
2. You don't have access to a FreeBSD 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.
Retrieve the following files (from _one_ ftp site to avoid any ver-
sion mismatches), and install them under /emul/freebsd (i.e.
foo/bar is installed as /emul/freebsd/foo/bar):
ldconfig and ldd don't necessarily need to be under /emul/freebsd,
you can install them elsewhere in the system too. Just make sure
they don't conflict with their NetBSD counterparts. A good idea
would be to install them in /usr/local/bin as ldconfig-freebsd and
Run the FreeBSD ldconfig program with directory arguments in which
the FreeBSD runtime linker should look for shared libs. /usr/lib
are standard, you could run like the following:
me@netbsd% mkdir -p /emul/freebsd/var/run
me@netbsd% touch /emul/freebsd/var/run/ld.so.hints
me@netbsd% ldconfig-freebsd /usr/X11R6/lib /usr/local/lib
Note that argument directories of ldconfig are mapped to
/emul/freebsd/XXXX by NetBSD's compat code, and should exist as such
on your system. Make sure /emul/freebsd/var/run/ld.so.hints is
existing when you run FreeBSD's ldconfig, if not, you may lose
NetBSD's /var/run/ld.so.hints. FreeBSD ldconfig should be stati-
cally linked, so it doesn't need any shared libraries by itself. It
will create the file /emul/freebsd/var/run/ld.so.hints. You should
rerun the FreeBSD version of the ldconfig program each time you add
a new shared library.
You should now be set up for FreeBSD binaries which only need a
shared libc. You can test this by running the FreeBSD ldd on
itself. Suppose that you have it installed as ldd-freebsd, it
should produce something like:
me@netbsd% ldd-freebsd `which ldd-freebsd`
-lc.2 => /usr/lib/libc.so.2.1 (0x1001a000)
This being done, you are ready to install new FreeBSD binaries.
Whenever you install a new FreeBSD program, you should check if it
needs shared libraries, and if so, whether you have them installed
in the /emul/freebsd tree. To do this, you run the FreeBSD 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 -l<majorname> => <fullname>.
If it prints ``not found'' instead of <fullname> it means that you
need an extra library. Which library this is, is shown in <major-
name>, which will be of the form XXXX.<N> You will need to find a
libXXXX.so.<N>.<mm> on a FreeBSD 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.
3. In some cases, FreeBSD binary needs access to certain device file.
For example, FreeBSD X server software needs FreeBSD /dev/ttyv0 for
ioctls. In this case, create a symbolic link from
/emul/freebsd/dev/ttyv0 to a wscons(4) device file like /dev/ttyE0.
You will need to have at least options WSDISPLAY_COMPAT_SYSCONS and
probably also options WSDISPLAY_COMPAT_USL in your kernel (see
options(4) and wscons(4)).
Finding the necessary files
Note: the information below is valid as of the time this document was
written (June, 1995), but certain details such as names of ftp sites,
directories and distribution names may have changed by the time you read
The FreeBSD distribution is 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:
Mirror sites are described on:
This distribution consists of a number of tar-ed and gzipped files, Nor-
mally, they're controlled by an install program, but you can retrieve
files ``by hand'' too. The way to look something up is to retrieve all
the files in the distribution, and ``tar ztvf'' through them for the file
you need. Here is an example of a list of files that you might need.
The files called ``bindist.??'' are tar-ed, gzipped and split, so you can
extract contents by ``cat bindist.?? | tar zpxf -''.
Extract the files from these gzipped tarfiles in your /emul/freebsd
directory (possibly omitting or afterwards removing files you don't
need), and you are done.
The information about FreeBSD distributions may become outdated.
BSD June 4, 1995 BSD