pre-install kernel hook: only keep 3 old kernels instead of waiting until we run out of disk space

kernel.d/pre-install/99-void-usb

@@ -1,24 +1,17 @@
 #!/usr/bin/env bash
 #
 # Kernel pre-install hook for Void-USB
-# This script removes old kernels when disk space is low.
+# This script removes old kernels to save disk space.
 #
 # Arguments: $1 package name, $2 kernel version
 PKGNAME="$1"
 VERSION="$2"
 
-MB_LOW=250
-MB_FREE="$(df --block-size=1M --output=avail /boot | tail -n1)"
+KEEP_OLD_KERNELS=3
 
-if [ "$MB_FREE" -lt "$MB_LOW" ]; then
-  echo
+while [ "$(vkpurge list | wc -l)" -gt "$KEEP_OLD_KERNELS" ]; do
   OLDEST_KERNEL="$(vkpurge list | sort | head -n1)"
-  if [ -z "$OLDEST_KERNEL" ]; then
-    echo -e "\033[31m================================================\n\033[33mWARNING:\033[0m Failed to find an old kernel to remove.\nThe /boot partition is running out of space.\nThis will become an issue if left unaddressed.\n\033[31m================================================\033[0m"
-  else
   echo "Removing old kernel $OLDEST_KERNEL using vkpurge..."
   vkpurge rm "$OLDEST_KERNEL"
   fi
-else
-  echo "Not doing anything, /boot has plenty of space."
-fi
+done

notes_to_self.txt

@@ -11,8 +11,6 @@ make our own or extract (if feasible) kb selection and time zone selection to hi
   - potentially interesting packages
     - ckbcomp
     - kbd-data
-vkpurge old stuff - only keep 2 vkpurgeable kernels
-  - change kernel pre-install hook
 overview of the installation process at the start
 overall progress indication (step x out of y)
 exclude optical drives