Upgrading from FreeBSD 3.X to FreeBSD 4.1-STABLE
Ralf S. Engelschall <rse@FreeBSD.org>
Version: 1.2 (2005-09-27)

ATTENTION: THIS UPGRADE PROCEDURE MIGHT NOT WORK FOR YOU AS YOUR
ENVIRONMENT IS DIFFERENT. ALSO, THIS UPGRADE PROCEDURES MIGHT DESTROY
YOUR SYSTEM AND YOU POTENTIALLY MIGHT LOOSE DATA.

o  boot the old FreeBSD 3.x in multi-user mode

o  provide a particular build environment
   $ vi /etc/make.conf
   NOPERL=true         # else Perl would fail to build under 3.x initially
   NOPROFILE=true      # to speed up building
   MAKE_RSAINTL=YES    # for non-US
   USA_RESIDENT=NO     # dito.
   CFLAGS=-O -pipe     # standard optimization
   COPTFLAGS=-O -pipe  # dito.
   COMPAT1X=yes        # install compatibility libraries
   COMPAT20=yes        # dito.
   COMPAT21=yes        # dito.
   COMPAT22=yes        # dito.
   COMPAT3X=yes        # dito.

o  provide boot-strapping run-time environment
   $ mkdir -p /usr/obj/usr/src/lib/libc
   $ ldconfig -R /usr/obj/usr/src/lib/libc

o  build the world initially (still under FreeBSD 3.x run-time)
   $ cd /usr/obj
   $ chflags -R noschg *
   $ rm -rf *
   $ cd /usr/src
   $ make buildworld

o  build and install new GENERIC kernel+modules
   $ make buildkernel KERNEL=GENERIC
   $ make installkernel KERNEL=GENERIC
   $ chflags noschg /kernel.GENERIC /GENERIC
   $ mv /kernel.GENERIC /kernel.GENERIC.3
   $ mv /GENERIC /kernel.GENERIC
   $ chflags schg /kernel.GENERIC

o  upgrade FOO kernel config from 3.x to 4.x
   $ vi /sys/i386/conf/FOO
   - remove "config kernel ...", "bio", "tty", "net", "conflicts"
   - remove unnecessary quotations
   - remove "pnp" device
   - remove "acd0" device
   - remove obsolete options (check output of "config FOO")
   - replace some "xxx0" with "xxx" (compare LINT for details)
   - replace "controller" & "disk" with "device"
   - replace "wdc0" with "ata0" plus more "ata*" from GENERIC
   - replace "bpfilter" with "bpf"
   - replace "isa?" with "atkbdc?" for "atkbd0" and "psm0" device
 
o  build and install new FOO kernel+modules
   $ make buildkernel KERNEL=FOO
   $ make installkernel KERNEL=FOO
   $ chflags noschg /kernel /FOO
   $ mv /kernel /kernel.3
   $ mv /FOO /kernel
   $ chflags schg /kernel

o  upgrade devices
   $ cd /usr/src/sbin/mknod && make install
   $ cp /usr/src/etc/MAKEDEV* /dev
   $ cd /dev 
   $ sh MAKEDEV all
   - make sure really all devices for disks exists:
     for N in the list of disks
       sh MAKEDEV N                   # eg ad0
       for M in the list of slices
           sh MAKEDEV NsMa            # eg ad0s1a
   - edit /etc/fstab and replace "wd0" with "ad0"

o  upgrade boot blocks and loader
   $ cd /sys/boot && make install

o  boot FreeBSD 4.x kernel (still with 3.x user-land) in single-user mode
   $ shutdown -r now
   > boot -s
   $ mount -a

o  install the world
   $ cd /usr/src/gnu/usr.bin/texinfo/install-info 
   $ make install
   $ ldconfig -R /usr/obj/usr/src/lib/libc
   $ cd /usr/src
   $ make installworld
   $ cd /usr/src/release/sysinstall && make all install

o  upgrade /etc
   $ cp -rp /etc /etc.old
   $ mergemaster -v -s

o  final adjustments for new FreeBSD 4.x user-land
   $ touch /var/log/security
   $ touch /var/log/cron
   $ rm /var/cron/log*

o  switch to new shipped OpenSSH [OPTIONAL!]
   $ ssh-keygen -f /etc/ssh/ssh_host_key
   $ ssh-keygen -d -f /etc/ssh/ssh_host_dsa_key
   $ vi /etc/rc.conf
   sshd_enable="YES"
   $ pkg_delete ssh-1.2.27

o  boot FreeBSD 4.x kernel and user-land in multi-user mode
   $ shutdown -r now

o  rebuild some criticial programs to avoid spurious segfaults
   under the forthcoming final "buildworld/installworld" step
   $ vi /etc/make.conf
   #NOPERL=true
   $ cd /usr/src/gnu/usr.bin/perl 
   $ (cd libperl && make all install)
   $ (cd perl && make all install)
   $ make clean all install
   $ cd /usr/src/usr.bin/lex && make clean all install
   $ cd /usr/src/usr.bin/yacc && make clean all install
   $ cd /usr/src/gnu/usr.bin/as && make clean all install
   $ cd /usr/src/gnu/usr.bin/cc && make clean all install
   $ cd /usr/src/gnu/lib/libgcc && make clean all install

o  build and install the world finally from scratch (under FreeBSD 4.x run-time)
   $ cd /usr/obj
   $ chflags -R noschg *
   $ rm -rf *
   $ cd /usr/src
   $ make buildworld
   $ make installworld

o  rebuild the kernel with the final tools
   $ cd /sys/i386/conf
   $ config FOO
   $ cd /sys/compile/FOO
   $ make depend all
   $ make install

o  reboot to switch to the final FreeBSD 4.x system
   $ shutdown -r now