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COMPAT_SVR4(8)          OpenBSD System Manager's Manual         COMPAT_SVR4(8)

     compat_svr4 - setup for running SVR4/iBCS2 binaries under emulation

     OpenBSD supports running SVR4/iBCS2 binaries.  This code has been tested
     on i386 and sparc systems.  Most programs should work, but not ones that
     use or depend on:

           kernel internal data structures
           the  /proc filesystem
           the ticotsord loopback rpc mechanism (NIS uses this)
           sound and video interfaces
           threads (ttsession uses threads)
           the streams administrative driver

     The SVR4 compatibility feature is active for kernels compiled with the
     COMPAT_SVR4 option and kern.emul.svr4 sysctl(8) enabled.

     Most SVR4 programs are dynamically linked.  This means that the shared
     libraries that the programs depend on and the runtime linker are also
     needed.  Additionally, a "shadow root" directory for SVR4 binaries on the
     OpenBSD system will have to be created.  This directory is named
     /emul/svr4.  Any file operations done by SVR4 programs run under OpenBSD
     will look in this directory first.  So, if a SVR4 program opens, for ex-
     ample, /etc/passwd, OpenBSD will first try to open /emul/svr4/etc/passwd,
     and if that does not exist open the `real' /etc/passwd file.  It is rec-
     ommended that SVR4 packages that include configuration files, etc., be
     installed under /emul/svr4, to avoid naming conflicts with possible
     OpenBSD counterparts.  Shared libraries should also be installed in the
     shadow tree.

     The simplest way to set up the system for SVR4 binaries is:
     1.   Make the necessary directories:

                (me@openbsd) mkdir -p /emul/svr4/{dev,etc}
                (me@openbsd) mkdir -p /emul/svr4/usr/{bin,lib}
                (me@openbsd) mkdir -p /emul/svr4/usr/openwin/{bin,lib}

     2.   Copy files from an SVR4 system:

                (me@svr4) cd /usr/lib
                (me@svr4) tar -cf - . | \
                     rsh openbsd 'cd /emul/svr4/usr/lib; tar -xpf -'

          If OpenWindows is going to be run:

                (me@svr4) cd /usr/openwin/lib
                (me@svr4) tar -cf - . | \
                     rsh openbsd 'cd /emul/svr4/usr/openwin/lib; tar -xpf -'

     3.   Set up the configuration files and devices:

                (me@openbsd) cd /usr/src/etc/etc.svr4
                (me@openbsd) cp netconfig nsswitch.conf /emul/svr4/etc
                (me@openbsd) cp SVR4_MAKEDEV /emul/svr4/dev
                (me@openbsd) cd /emul/svr4/dev; sh SVR4_MAKEDEV all

     An alternative method is to mount a whole SVR4 partition in /emul/svr4
     and then override with other mounts /emul/svr4/etc and /emul/svr4/dev.

     Clearly, a complete SVR4 /dev directory cannot be used as /emul/svr4/dev,
     because other device nodes, such as /dev/null, need to be OpenBSD device

     Many system calls are still not emulated.  The streams emulation is in-
     complete (socketpair does not work yet).

     Most SVR4 executables can not handle directory offset cookies > 32 bits.
     More recent ones, compiled for large file support (Solaris 2.6 and up)
     can.  With older programs, the message "svr4_getdents: dir offset too
     large for emulated program" will appear when this happens.  Currently,
     this can only happen on NFS mounted filesystems, 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 filesystem with
     the -2 option to mount_nfs(8).

OpenBSD 3.6                      July 6, 1996                                2