BackTrack With Ubuntu USB Key

I have a USB key with several Linux distro: BackTrack, Ubuntu, Slax, some recovery distros, ... All Working with persistent changes.
It's quite easy to have pleinty of distro on one USB key with a syslinux start menu to boot them. But some like Ubuntu and BackTrack 4 are using squashfs filesystem in a casper folder, and it is more difficult to make them work together.
For ubuntu, the Live Initrd has an option to specify the location of the casper folder. Since i decompressed ubuntu live cd in an ubuntu folder on my usb key, i added these options to syslinux:

ignore_uuid live-media-path=/ubuntu/casper

BackTrack's initrd does not support this parameter so you must have to patch it:

mkdir tmp
# put initrd.gz from BackTrack iso to tmp folder
cd tmp
gzip -dc initrd.gz | cpio -id
rm initrd.gz
patch -u scripts/casper < ../casper.patch
find . | cpio --quiet --dereference -o -H newc | gzip -9 > ../initrd-patched.gz

Then in your syslinux entry, use the new initrd-patched.gz instead of the original one.

The patched initrd image can be downloaded here. You can then use these parameters in your syslinux entry for BackTrack:

ignore_uuid live-media-path=/backtrack/casper

casper.patch:

--- tmp/scripts/casper 2010-01-11 22:15:21.464236536 -0500
+++ casper 2010-01-11 22:19:23.039237990 -0500
@@ -5,6 +5,7 @@
 export PATH=/usr/bin:/usr/sbin:/bin:/sbin
 
 mountpoint=/cdrom
+LIVE_MEDIA_PATH=casper
 
 root_persistence="casper-rw"
 home_persistence="home-rw"
@@ -44,6 +45,10 @@
                 export STATICIP ;;
             ignore_uuid)
                 IGNORE_UUID="Yes" ;;
+            live-media-path=*)
+                LIVE_MEDIA_PATH="${x#live-media-path=}"
+                export LIVE_MEDIA_PATH
+                echo "export LIVE_MEDIA_PATH=\"$LIVE_MEDIA_PATH\"" >> /etc/casper.conf ;;
         esac
     done
     if [ "${UNIONFS}" = "" ]; then
@@ -53,10 +58,10 @@
 
 is_casper_path() {
     path=$1
-    if [ -d "$path/casper" ]; then
-        if [ "$(echo $path/casper/*.squashfs)" != "$path/casper/*.squashfs" ] ||
-            [ "$(echo $path/casper/*.ext2)" != "$path/casper/*.ext2" ] ||
-            [ "$(echo $path/casper/*.dir)" != "$path/casper/*.dir" ]; then
+    if [ -d "$path/$LIVE_MEDIA_PATH" ]; then
+        if [ "$(echo $path/$LIVE_MEDIA_PATH/*.squashfs)" != "$path/$LIVE_MEDIA_PATH/*.squashfs" ] ||
+            [ "$(echo $path/$LIVE_MEDIA_PATH/*.ext2)" != "$path/$LIVE_MEDIA_PATH/*.ext2" ] ||
+            [ "$(echo $path/$LIVE_MEDIA_PATH/*.dir)" != "$path/$LIVE_MEDIA_PATH/*.dir" ]; then
             return 0
         fi
     fi
@@ -106,10 +111,10 @@
 mount_images_in_directory() {
     directory="$1"
     rootmnt="$2"
-    if match_files_in_dir "$directory/casper/*.squashfs" ||
-        match_files_in_dir "$directory/casper/*.ext2" ||
-        match_files_in_dir "$directory/casper/*.dir"; then
-        setup_unionfs "$directory/casper" "$rootmnt"
+    if match_files_in_dir "$directory/$LIVE_MEDIA_PATH/*.squashfs" ||
+        match_files_in_dir "$directory/$LIVE_MEDIA_PATH/*.ext2" ||
+        match_files_in_dir "$directory/$LIVE_MEDIA_PATH/*.dir"; then
+        setup_unionfs "$directory/$LIVE_MEDIA_PATH" "$rootmnt"
     else
         :
     fi
@@ -415,11 +420,11 @@
 
     if [ -n "${SHOWMOUNTS}" ]; then
         for d in ${rofslist}; do
-            mkdir -p "${rootmnt}/casper/${d##*/}"
+            mkdir -p "${rootmnt}/${LIVE_MEDIA_PATH}/${d##*/}"
             case d in
-                *.dir) # do nothing # mount -o bind "${d}" "${rootmnt}/casper/${d##*/}"
+                *.dir) # do nothing # mount -o bind "${d}" "${rootmnt}/${LIVE_MEDIA_PATH}/${d##*/}"
                     ;;
-                *) mount -o move "${d}" "${rootmnt}/casper/${d##*/}"
+                *) mount -o move "${d}" "${rootmnt}/${LIVE_MEDIA_PATH}/${d##*/}"
                     ;;
             esac
         done

2009-01-18 Update request

I was requested to give as example my syslinux config files. Here is the root filesystem of my usb key:

kha@box:/media/usbsys$ ls
backtrack  clonezilla  g4l  gparted  other  slax  slitaz  syslinux  sysrescue  ubcd  ubuntu
kha@box:/media/usbsys$

I have setup syslinux hidden boot file into the syslinux folder. The content of my syslinux folder can be downloaded from here.

Here is a preview of my bootable syslinux menu: