Remastering dCore is pretty much the same as Core. dCorePlus is basically a remastered dCore, extensions in a remaster go in /tmp/builtin. They can in a directory named /cde at the root of the CD for a cdrom image.
The existing remastering tools could be modified to work with dCore, but so far there has not been much demand for it.
What I do when packing and unpacking dCore images is use a simple script and make the changes to the files within them. To unpack an image, I use the below script named dCoreunpack.sh with the usage "dCoreunpack.sh dCore-trusty.gz" to unpack dCore-trusty.gz into a rootfs directory:
#!/bin/sh
CORE="$1"
if [ ! -d rootfs ]; then
mkdir rootfs
else
rm -r rootfs/*
fi
cd rootfs
zcat ../"$CORE" | cpio -i -H newc -d
cd -
Then to repack, I use the below with the name dCorepack.sh and the usage "dCorepack.sh dCore-trusty.gz" to repack dCore-trusty.gz:
#!/bin/sh
CORE="$1"
REPO=`cat rootfs/usr/share/doc/tc/repo.txt`
RELEASE=`echo dCore-"$REPO":$(date "+%Y.%m.%d.%H.%M")`
echo "$RELEASE" > rootfs/usr/share/doc/tc/release.txt
echo "$RELEASE" > dCore-"$REPO".latest
cd rootfs
find | cpio -o -H newc | gzip -2 > ../"$CORE"
cd ..
md5sum "$CORE" > "$CORE".md5.txt
cd -
These scripts should be run with root privileges.