NOTE: This post is old. I no longer generate mfsroots in this fashion and my methods continue to evolve, but my latest approach to modifying mfsroots is documented in the Installing FreeBSD via Cobbler post.

Automating Generation of the mfsroot.gz

#! /bin/sh
# 
# mkmfsroot.sh:   Generate a FreeBSD mfsroot file.  This script does not
#                 function on hosts that are not running FreeBSD.
# 
# Author:   Rick
# Date:     21 August 2012
# Modif:

#####
## Variables
#####
      
SELF="${0##*/}";
NULL="/dev/null";
TMP="/tmp";
PATH="${PATH}";
ZERO="/dev/zero";
MFSROOTDIR="${1}";
SVNREPO="https://dummy.subversion.com/ats/ad/freebsd-prov/mfsroot/${MFSROOTDIR}";
REPODIR="/data/freebsd-prov/mfsroot/${MFSROOTDIR}";
MFSROOTSTAND="${REPODIR}/stand";
SVN="/usr/local/bin/svn";
STANDFILES="doconfig.sh install.cfg boot_crunch";
MFSROOT="/tmp/mfsroot";
MFSROOTMNT="/tmp/mfsrootmnt";

#####
## Functions
#####

# Clean what this script has done
CLEANUP() {

   [ "${MDCFG}" = "True" ] && mdconfig -d -u ${DEVNUM};

   if [ -d ${MFSROOTMNT} ]; then
      cd && umount ${MFSROOTMNT} > ${NULL} 2>&1;
      rm -rf ${MFSROOTMNT};
   fi
   [ -e ${MFSROOT} ] && rm ${MFSROOT};
   [ -e ${REPODIR} ] && rm -rf ${REPODIR};
   
}

# We are erroring and exiting the script
ERR_EXIT() {

   echo "${1}" 1>&2;
   CLEANUP;
   exit 1;

}

#####
## Main
#####

# Force two command line arguments
[ -z ${1} ] && ERR_EXIT "Specify an mfsroot!";

# Verify we're on a FreeBSD host
HOSTOS=`uname -s`;
[ ${HOSTOS} != "FreeBSD" ] && ERR_EXIT "Build host is not FreeBSD! Exiting!";

# Ensure we're using the latest repo version
[ -d ${REPODIR} ] && rm -rf ${REPODIR};
${SVN} export ${SVNREPO} ${REPODIR};

# Does the mfsroot dir we asked for exist?
[ ! -d ${REPODIR} ] && ERR_EXIT "${1} does not exist! Exiting!";

# Remove .svn if it exists
[ -d ${REPODIR}/.svn ] && rm -rf ${REPODIR}/.svn

# Fix stand/
#
# What do we do here and why?
#
# Since the contents of the mfsroot are stored in subversion, when the content
# is checked out or exported, each of the files in stand/ are stored as
# individual files when they are actually supposed to be hardlinks back to
# boot_crunch.  Therefore, the code below checks out the content, removes the
# files in stand/, and exports boot_crunch and a couple other scripts.  It
# finishes by regenerating all the hardlinks back to boot_crunch.
#
# We could resolve this in any number of ways, but as a stop gap measure for
# now we will leave it this way and fix it in the future.
if [ -d ${MFSROOTSTAND} ]; then
   rm ${MFSROOTSTAND}/*;
   for ea in ${STANDFILES}; do
      ${SVN} export ${SVNREPO}/stand/${ea} ${MFSROOTSTAND};
   done
 
   cd ${MFSROOTSTAND};
   for i in $(./boot_crunch 2>&1 | grep -v usage); do
      if [ "$i" != "boot_crunch" ]; then
         rm -f ./"$i";
         ln ./boot_crunch "$i";
      fi
   done
fi

# Calculate the size of the mfsroot, prepare the file and populate it
MFSROOTSIZE=$(du -sk ${REPODIR} | awk '{ print $1 }');
[ -z ${MFSROOTSIZE} ] && ERR_EXIT "Unable to determine mfsroot size! Exiting!";

dd if=${ZERO} of=${MFSROOT} bs=1024 count=$((${MFSROOTSIZE} + 1024));
[ $? -ge 1 ] && ERR_EXIT "Unable to create ${MFSROOT}! Exiting!";

MFSROOTDEV=$(mdconfig -f ${MFSROOT});
[ -z ${MFSROOTDEV} ] && ERR_EXIT "Unable to mount ${MFSROOT}! Exiting!";
DEVNUM=$(echo ${MFSROOTDEV} | awk '{ print substr($0,length($0)-0,length($0)) }'
);
MDCFG="True";

newfs /dev/${MFSROOTDEV};

[ ! -d ${MFSROOTMNT} ] && mkdir ${MFSROOTMNT};
mount /dev/${MFSROOTDEV} ${MFSROOTMNT} && \
   (cd ${REPODIR}; tar -cf - .) | (cd ${MFSROOTMNT}; tar -xf -);
   
# Now the new mfsroot has been populated, it's time to save it and clean up
umount ${MFSROOTMNT} && mdconfig -d -u ${DEVNUM} && gzip ${MFSROOT};
[ $? -ne 0 ] && ERR_EXIT "Error unmounting ${MFSROOT}! Exiting!";
MDCFG="False";
CLEANUP;
         
#####
## EOF
#####