Идея заключается чтобы для каждой компоненты-стадии
(boot, disk, install2, live, rescue,.....)
можно было указывать в ее конфигурацонном файле ($IDENT/config)
тип желаемого образа на выходе (tgz, tbz2, cpio, squashfs) например:
IMAGE_TYPE="cpio"

Вот наброс патча:

--- spt 2007-03-14 03:35:43 +0300
+++ my-spt  2007-04-05 13:38:20 +0400
@@ -37,8 +37,10 @@

 create_image() {
    Verbose "Creating image for \`$IDENT'."
+    [ -n "$IMAGE_TYPE" ] || IMAGE_TYPE="$image_type"
+    Verbose "image type: \`$IMAGE_TYPE'."

-   case "$image_type" in
+   case "$IMAGE_TYPE" in
        squashfs)
        init_chroot_progs "squashfsprogs"
        cp -a "$tmpdir/.archive.tar" "$chroot/tmp/"
@@ -57,6 +59,20 @@
        mkiso=
        cat "$tmpdir/.archive.tar" | gzip -f9 > "$workdir/$OUT.tar.gz"
        ;;
+        cpio)
+        init_chroot_progs "cpio findutils"
+       cp -a "$tmpdir/.archive.tar" "$chroot/tmp/"
+cat >"$tmpdir/script" <<'__EOF__'
+mkdir -p /tmp/.archive
+tar -C /tmp/.archive -xf /tmp/.archive.tar
+cd /tmp/.archive
+find . | cpio -o -H newc > /.image
+__EOF__
+       chroot_exec "$tmpdir/script"
+       mv -f -- "$chroot/.image" "$outdir/$OUT"
+        gzip "$outdir/$OUT"
+        mv "$outdir/$OUT.gz" "$outdir/$OUT"
+        ;;
        *)
        Fatal 'Unsupported image type.'
        ;;
@@ -115,7 +132,7 @@

    if [ -n "$HOOKPKGS" ]; then
        Verbose "Installation packages for hook"
-       hsh-install "$workdir" $verbose $quiet $excludedocs
${number:+--number="$number"} 
$HOOKPKGS
+       hsh-install "$workdir" $verbose $quiet $excludedocs
${number:+--number="$number"} 
--save-fakeroot $HOOKPKGS
    fi

    packages="$profile_dir/$IDENT/packages"
@@ -151,12 +168,12 @@

 runto_components() {
     local cmd comp
-    local IDENT VENDOR COPYONLY INSTALLDIR NOIMAGE EXTRAOPTS FILES OUT
+    local IDENT VENDOR COPYONLY INSTALLDIR NOIMAGE EXTRAOPTS FILES OUT IMAGE_TYPE

     cmd="$1" && shift

     for comp in $COMPONENTS; do
-   IDENT="packages" VENDOR="ALTLinux" COPYONLY= INSTALLDIR= NOIMAGE= EXTRAOPTS=
FILES= OU
T=
+   IDENT="packages" VENDOR="ALTLinux" COPYONLY= INSTALLDIR= NOIMAGE= EXTRAOPTS=
FILES= OU
T= IMAGE_TYPE=

    . "$profile_dir/$comp/config" ||
        Fatal "File \`$profile_dir/$comp/config' not found."