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NetBSD 6.1.5 - man page for compat_linux (netbsd section 8)

COMPAT_LINUX(8) 		   BSD System Manager's Manual			  COMPAT_LINUX(8)

NAME
     compat_linux -- setup procedure for running Linux binaries

DESCRIPTION
     NetBSD supports running Linux binaries.  This applies to amd64, arm, alpha, i386, m68k, and
     powerpc systems for now.  Both the a.out and ELF binary formats are supported.  Most pro-
     grams should work, including the ones that use the Linux SVGAlib (only on i386).  NetBSD
     amd64 can execute both 32bit and 64bit linux programs.  Programs that will not work include
     some that use i386-specific calls, such as enabling virtual 8086 mode.  Currently, sound is
     only partially supported for Linux binaries (they will probably run, depending on what Linux
     sound support features are used).

     The Linux compatibility feature is active for kernels compiled with the COMPAT_LINUX option
     enabled.  If support for Linux a.out executables is desired, the EXEC_AOUT option should be
     enabled in addition to option COMPAT_LINUX.  Similarly, if support for Linux 32-bit and/or
     64-bit ELF executables is desired, the EXEC_ELF32 and/or EXEC_ELF64 options (respectively)
     should be enabled in addition to COMPAT_LINUX.

     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 NetBSD system.  This direc-
     tory is named /emul/linux or /emul/linux32 for 32bit emulation on 64bit systems.  Any file
     operations done by Linux programs run under NetBSD will look in this directory first.  So,
     if a Linux program opens, for example, /etc/passwd, NetBSD 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 NetBSD counterparts.	Shared libraries
     should also be installed in the shadow tree.  Filenames that start "/../" are only looked up
     in the real root.

     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 NetBSD 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.

   Setting up shared libraries
     How to get to know which shared libraries Linux binaries need, and where to get them? Basi-
     cally, 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.   For i386, you can simply install the SuSE shared libs using the
	  pkgsrc/emulators/suse100_linux package(s).  On PowerPC ports, the
	  pkgsrc/emulators/linuxppc_lib will install the needed libraries.  If you are on other
	  platforms, or this doesn't supply you with all the needed libraries, read on.

     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 NetBSD system.  Exam-
	  ple: 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':

		(me@linux) ldd linuxxdoom
		     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

	  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 NetBSD system:
	  /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)

	  Note that if you already have a Linux shared library with a matching major revision
	  number to the first column of the ldd(1) 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 advis-
	  able 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:

	  /emul/linux/lib/libc.so.4.6.27
	  /emul/linux/lib/libc.so.4 -> /emul/linux/lib/libc.so.4.6.27

	  and you find that the ldd output for a new binary you want to install is:

	  libc.so.4 (DLL Jump 4.5pl26) => /lib/libc.so.4.6.29

	  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:
	  /emul/linux/lib/libc.so.4.6.29
	  /emul/linux/lib/libc.so.4 -> /emul/linux/lib/libc.so.4.6.29

	  Please note that the symbolic link mechanism is only needed for Linux binaries, the
	  NetBSD runtime linker takes care of looking for matching major revision numbers itself,
	  you don't need to worry about that.

	  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 NetBSD system (in the /emul/linux tree):
	  /lib/ld.so
	  /etc/ld.so.cache
	  /etc/ld.so.config

     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.

	  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):

	  /sbin/ldconfig
	  /usr/bin/ldd
	  /lib/libc.so.x.y.z
	  /lib/ld.so

	  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 NetBSD
	  counterparts.  A good idea would be to install them in /usr/local/bin as ldconfig-linux
	  and ldd-linux.

	  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 fol-
	  lowing:
	  /usr/X11/lib
	  /usr/local/lib

	  Note that these are mapped to /emul/linux/XXXX by NetBSD's compat code, and should
	  exist as such on your system.

	  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 ldconfig each time you add a new shared library.

	  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:

		(me@netbsd) ldd-linux `which ldd-linux`
		     libc.so.4 (DLL Jump 4.5pl26) => /lib/libc.so.4.6.29

	  This being 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 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>.

	  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.

     4.   Set up linux specific devices:

		(me@netbsd) cd /usr/share/examples/emul/linux/etc
		(me@netbsd) cp LINUX_MAKEDEV /emul/linux/dev
		(me@netbsd) cd /emul/linux/dev && sh LINUX_MAKEDEV all

   Setting up procfs
     Some Linux binaries expect procfs to be mounted and that it would contain some Linux spe-
     cific stuff.  If it's not the case, they behave unexpectedly or even crash.

     Mount procfs on NetBSD using following command:

	   (me@netbsd) mount_procfs -o linux procfs /emul/linux/proc

     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 /etc/fstab.

	   procfs /emul/linux/proc procfs ro,linux

     See mount_procfs(8) for further information.

   Setting up other files
     Newer version of Linux use /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 /emul/linux/etc.

   Finding the necessary files
     Note: the information below is valid as of the time this document was first 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.

     Linux is distributed by several groups that make their own set of binaries that they dis-
     tribute.  Each distribution has its own name, like ``Slackware'' or ``Yggdrasil''.  The dis-
     tributions 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, usu-
     ally consisting of subdirectories with gzipped tar files in them.	The primary ftp sites for
     the distributions are:
	   sunsite.unc.edu:/pub/Linux/distributions
	   tsx-11.mit.edu:/pub/linux/distributions

     Some European mirrors:
	   ftp.luth.se:/pub/linux/distributions
	   ftp.demon.co.uk:/pub/linux/distributions
	   src.doc.ic.ac.uk:/packages/linux/distributions

     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:

	   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

     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:

	   Package		   Location

	   ldso 		   diska2
	   shlibs		   diska2
	   oldlibs		   diskx6
	   xf_lib		   diskx9

     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):
     slakware/a2/ldso.tgz
     slakware/a2/shlibs.tgz
     slakware/x6/oldlibs/tgz
     slakware/x9/xf_lib.tgz

     Extract the files from these gzipped tarfiles in your /emul/linux directory (possibly omit-
     ting or afterwards removing files you don't need), and you are done.

   Programs using SVGAlib
     SVGAlib binaries require some extra care.	You need to have options WSDISPLAY_COMPAT_USL in
     your kernel (see wscons(4)), and you will also have to create some symbolic links in the
     /emul/linux/dev directory, namely:
     /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

     Be warned: the first link mentioned here makes SVGAlib binaries work, but may confuse oth-
     ers, so you may have to remove it again at some point.

BUGS
     The information about Linux distributions may become outdated.

     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.

     Linux executables cannot handle directory offset cookies > 32 bits.  Should such an offset
     occur, you will see the message ``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 -X option to mount_nfs(8).  The -2 option to mount_nfs(8) will also have
     the desired effect, but is less preferable.

BSD					  April 30, 2007				      BSD


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