diff --git a/README.md b/README.md
index c655aa48..7bc176cd 100644
--- a/README.md
+++ b/README.md
@@ -536,7 +536,7 @@ remove packages specified in `filesystem.manifest` that are *not* listed in `fil
 6. Generate md5sum.txt
 
    ```shell
-   /bin/bash -c "(find . -type f -print0 | xargs -0 md5sum | grep -v -e 'md5sum.txt' -e 'bios.img' -e 'efiboot.img' > md5sum.txt)"
+   /bin/bash -c "(find . -type f -print0 | xargs -0 md5sum | grep -v -e 'isolinux' > md5sum.txt)"
    ```
 
 ### Cleanup the chroot environment
diff --git a/scripts/chroot_build.sh b/scripts/chroot_build.sh
index 026e4ebf..5d69833d 100755
--- a/scripts/chroot_build.sh
+++ b/scripts/chroot_build.sh
@@ -279,7 +279,7 @@ EOF
     cat /usr/lib/grub/i386-pc/cdboot.img isolinux/core.img > isolinux/bios.img
 
     # generate md5sum.txt
-    /bin/bash -c "(find . -type f -print0 | xargs -0 md5sum | grep -v -e 'md5sum.txt' -e 'bios.img' -e 'efiboot.img' > md5sum.txt)"
+    /bin/bash -c "(find . -type f -print0 | xargs -0 md5sum | grep -v -e 'isolinux' > md5sum.txt)"
 
     popd # return initial directory
 }
diff --git a/scripts/default_config.sh b/scripts/default_config.sh
index 964377b6..5797a228 100644
--- a/scripts/default_config.sh
+++ b/scripts/default_config.sh
@@ -7,7 +7,7 @@
 
 # The version of Ubuntu to generate.  Successfully tested LTS: bionic, focal, jammy, noble
 # See https://wiki.ubuntu.com/DevelopmentCodeNames for details
-export TARGET_UBUNTU_VERSION="noble"
+export TARGET_UBUNTU_VERSION="focal"
 
 # The Ubuntu Mirror URL. It's better to change for faster download.
 # More mirrors see: https://launchpad.net/ubuntu/+archivemirrors