Thanks to @Anon on Unix.SE for the pointer on how to do this. And to @Andy‘s comment on @mmckinst‘s answer for the warning about additional packages you may need.
As my three readers know, I run a CentOS mirror. One of the idiosyncrasies of CentOS, like its upstream RHEL, is that DVD ISOs aren’t always just one image – for example, the 6.6 x64 image comes on two ISOs. I suppose this has something to do with the “normal” or “simple” capacity of a DVD disc, but it’s annoying.
Enter the mkdvdiso.sh script (original found here) from Chris Kloiber & Phil Schaffner.
The process I used to combine these two ISOs into one is as follows:
yum install isomd5sum createrepo mkisofs
mkdvdiso.sh /full/path/to/original/isos /full/path/to/destination.iso
For posterity, and in case the CentOS wiki dies, below is the mkdvdiso.sh script:
#!/bin/bash
# by Chris Kloiber
# Mods under CentOS by Phil Schaffner
# A quick hack that will create a bootable DVD iso of a Red Hat Linux
# Distribution. Feed it either a directory containing the downloaded
# iso files of a distribution, or point it at a directory containing
# the "RedHat", "isolinux", and "images" directories.
# This version only works with "isolinux" based Red Hat Linux versions.
# Lots of disk space required to work, 3X the distribution size at least.
# GPL version 2 applies. No warranties, yadda, yadda. Have fun.
# Modified to add sanity checks and fix CentOS4 syntax errors
# TODO:
# Add checks for available disk space on devices holding output and
# temp files.
# Add optional 3rd parameter to specify location of temp directory.
# Create .discinfo if not present.
OS_VER=\
$((test -e /etc/fedora-release && rpm -qf /etc/fedora-release --qf "FC%{VERSION}") \
|| (test -e /etc/redhat-release && rpm -qf /etc/redhat-release --qf "EL%{VERSION}") \
|| echo OS_unknown)
case "$OS_VER" in
EL[45]*|FC?)
IMPLANT=/usr/lib/anaconda-runtime/implantisomd5
if [ ! -f $IMPLANT ]; then
echo "Error: $IMPLANT Not Found!"
echo "Please install anaconda-runtime and try again."
exit 1
fi
;;
EL6*|FC1?)
IMPLANT=/usr/bin/implantisomd5
if [ ! -f $IMPLANT ]; then
echo "Error: $IMPLANT Not Found!"
echo "Please install isomd5sum and try again."
exit 1
fi
;;
OS_unknown)
echo "Unknown OS."
exit 1
;;
*)
echo "Fix this script for $OS_VER"
exit 1
esac
if [ $# -lt 2 ]; then
echo "Usage: `basename $0` source /destination/DVD.iso"
echo ""
echo " The 'source' can be either a directory containing a single"
echo " set of isos, or an exploded tree like an ftp site."
exit 1
fi
DVD_DIR=`dirname $2`
DVD_FILE=`basename $2`
echo "DVD directory is $DVD_DIR"
echo "ISO file is $DVD_FILE"
if [ "$DVD_DIR" = "." ]; then
echo "Destinaton Directory $DVD_DIR does not exist"
exit 1
else
if [ ! -d "/$DVD_DIR" ]; then
echo "Destinaton Directory $DVD_DIR must be an absolute path"
exit 1
else
if [ "$DVD_FILE" = "" ] || [ -d "$DVD_DIR/$DVD_FILE" ]; then
echo "Null ISO file name."
exit 1
fi
fi
fi
which mkisofs >&/dev/null
if [ "$?" != 0 ]; then
echo "mkisofs Not Found"
echo "yum install mkisofs"
fi
which createrepo >&/dev/null
if [ "$?" != 0 ]; then
echo "createrepo Not Found"
echo "yum install createrepo"
fi
if [ -f $2 ]; then
echo "DVD ISO destination $2 already exists. Remove first to recreate."
exit 1
fi
# Make sure there is enough free space to hold the DVD image on the filesystem
# where the home directory resides, otherwise change ~/mkrhdvd to point to
# a filesystem with sufficient free space.
cleanup() {
[ ${LOOP:=/tmp/loop} = "/" ] && echo "LOOP mount point = \/, dying!" && exit
[ -d $LOOP ] && rm -rf $LOOP
[ ${DVD:=~/mkrhdvd} = "/" ] && echo "DVD data location is \/, dying!" && exit
[ -d $DVD ] && rm -rf $DVD
}
cleanup
mkdir -p $LOOP
mkdir -p $DVD
ls $1/*.iso &>/dev/null
if [ "$?" = 0 ]; then
echo "Found ISO CD images..."
CDS=`expr 0`
DISKS="1"
[ -w / ] || { # Very portable, but perhaps not perfect, test for superuser.
echo "Only 'root' may use this script for loopback mounts" 1>&2
exit 1
}
for f in `ls $1/*.iso`; do
mount -o loop $f $LOOP
cp -av $LOOP/* $DVD
if [ -f $LOOP/.discinfo ]; then
cp -av $LOOP/.discinfo $DVD
CDS=`expr $CDS + 1`
if [ $CDS != 1 ] ; then
DISKS=`echo ${DISKS},${CDS}`
fi
fi
umount $LOOP
done
else
if [ -f $1/isolinux/isolinux.bin ]; then
echo "Found FTP-like tree..."
if [ -e $1/.discinfo ]; then
cp -av $1/.discinfo $DVD
else
# How does one construct a legal .discinfo file if none is found?
echo "Error: No .discinfo file found in $1"
cleanup
exit 1
fi
cp -av $1/* $DVD
else
echo "Error: No CD images nor FTP-like tree found in $1"
cleanup
exit 1
fi
fi
if [ -e $DVD/.discinfo ]; then
awk '{ if ( NR == 4 ) { print disks } else { print ; } }' disks="ALL" $DVD/.discinfo > $DVD/.discinfo.new
mv $DVD/.discinfo.new $DVD/.discinfo
else
echo "Error: No .discinfo file found in $DVD"
cleanup
exit 1
fi
rm -rf $DVD/isolinux/boot.cat
find $DVD -name TRANS.TBL | xargs rm -f
cd $DVD
createrepo -g repodata/comps.xml ./
mkisofs -J -R -v -T -o $2 -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 8 -boot-info-table $DVD
if [ "$?" = 0 ]; then
echo ""
echo "Image complete, create md5sum..."
# $IMPLANT --force $2
# Don't like forced mediacheck? Try this instead.
$IMPLANT --supported-iso --force $2
echo "Start cleanup..."
cleanup
echo ""
echo "Process Complete!"
echo "Wrote DVD ISO image to $DVD_DIR/$DVD_FILE"
echo ""
else
echo "ERROR: Image creation failed, start cleanup..."
cleanup
echo ""
echo "Failed to create ISO image $DVD_DIR/$DVD_FILE"
echo ""
fi