diff --git a/src/install.sh b/src/install.sh
index ae36972..098881a 100644
--- a/src/install.sh
+++ b/src/install.sh
@@ -3,36 +3,41 @@ set -Eeuo pipefail
 
 # Check if running with interactive TTY or redirected to docker log
 if [ -t 1 ]; then
-  PROGRESS="--progress=bar:noscroll"
+  progress="--progress=bar:noscroll"
 else
-  PROGRESS="--progress=dot:giga"
+  progress="--progress=dot:giga"
 fi
 
-BASE=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.iso -printf "%f\n" | head -n 1)
-[ -z "$BASE" ] && BASE=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.img -printf "%f\n" | head -n 1)
+file="/boot.iso" && [ -f "$file" ] && [ -s "$file" ] && BOOT="$file" && return 0
+file="/boot.img" && [ -f "$file" ] && [ -s "$file" ] && BOOT="$file" && return 0
 
-[ -f "$STORAGE/$BASE" ] && return 0
+file=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.iso -printf "%f\n" | head -n 1)
+[ -z "$file" ] && file=$(find "$STORAGE" -maxdepth 1 -type f -iname boot.img -printf "%f\n" | head -n 1)
+[ -n "$file" ] && file="$STORAGE/$file" 
+[ -f "$file" ] && [ -s "$file" ] && BOOT="$file" && return 0
 
 if [ -z "$BOOT" ]; then
   error "No boot disk specified, set BOOT= to the URL of an ISO file." && exit 64
 fi
 
-BASE=$(basename "$BOOT")
-[ -f "$STORAGE/$BASE" ] && return 0
+base=$(basename "$BOOT")
+[ -n "$base" ] && file="$STORAGE/$base" 
+[ -f "$file" ] && [ -s "$file" ] && BOOT="$file" && return 0
 
-BASE=$(basename "${BOOT%%\?*}")
-: "${BASE//+/ }"; printf -v BASE '%b' "${_//%/\\x}"
-BASE=$(echo "$BASE" | sed -e 's/[^A-Za-z0-9._-]/_/g')
-[ -f "$STORAGE/$BASE" ] && return 0
+base=$(basename "${BOOT%%\?*}")
+: "${base//+/ }"; printf -v base '%b' "${_//%/\\x}"
+base=$(echo "$base" | sed -e 's/[^A-Za-z0-9._-]/_/g')
+[ -n "$base" ] && file="$STORAGE/$base" 
+[ -f "$file" ] && [ -s "$file" ] && BOOT="$file" && return 0
 
-TMP="$STORAGE/${BASE%.*}.tmp"
+TMP="$STORAGE/${base%.*}.tmp"
 rm -f "$TMP"
 
-MSG="Downloading $BASE..."
-info "$MSG" && html "$MSG"
+msg="Downloading $base..."
+info "$msg" && html "$msg"
 
-/run/progress.sh "$TMP" "" "Downloading $BASE ([P])..." &
-{ wget "$BOOT" -O "$TMP" -q --timeout=10 --show-progress "$PROGRESS"; rc=$?; } || :
+/run/progress.sh "$TMP" "" "Downloading $base ([P])..." &
+{ wget "$BOOT" -O "$TMP" -q --timeout=10 --show-progress "$progress"; rc=$?; } || :
 
 fKill "progress.sh"
 
@@ -41,12 +46,12 @@ fKill "progress.sh"
 
 html "Download finished successfully..."
 
-SIZE=$(stat -c%s "$TMP")
+size=$(stat -c%s "$TMP")
 
-if ((SIZE<100000)); then
+if ((size<100000)); then
   error "Invalid ISO file: Size is smaller than 100 KB" && exit 62
 fi
 
-mv -f "$TMP" "$STORAGE/$BASE"
+mv -f "$TMP" "$file"
 
 return 0