diff --git a/Dockerfile b/Dockerfile
index 65a3db6..e675a11 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.14 b/Dockerfile.3.14
index 7d64505..49e79eb 100644
--- a/Dockerfile.3.14
+++ b/Dockerfile.3.14
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.15 b/Dockerfile.3.15
index 2ead424..11154ed 100644
--- a/Dockerfile.3.15
+++ b/Dockerfile.3.15
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.16 b/Dockerfile.3.16
index 1d36d45..e7e0183 100644
--- a/Dockerfile.3.16
+++ b/Dockerfile.3.16
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.17 b/Dockerfile.3.17
index a3c37bc..2028c04 100644
--- a/Dockerfile.3.17
+++ b/Dockerfile.3.17
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.18 b/Dockerfile.3.18
index 7e94ce7..51a37df 100644
--- a/Dockerfile.3.18
+++ b/Dockerfile.3.18
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.19 b/Dockerfile.3.19
index 84bd1c1..9a7aa7c 100644
--- a/Dockerfile.3.19
+++ b/Dockerfile.3.19
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]
diff --git a/Dockerfile.3.20 b/Dockerfile.3.20
index 387a53b..61bd665 100644
--- a/Dockerfile.3.20
+++ b/Dockerfile.3.20
@@ -70,9 +70,11 @@ WORKDIR /root
 RUN set -e; \
   echo "Setting up prerequisites"; \
   apk --no-cache add bash; \
-  BASH_CMD="$(command -v bash 2>/dev/null|| true)"; \
-  [ -x "$BASH_CMD" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true; \
-  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true
+  SH_CMD="$(which sh 2>/dev/null)"; \
+  BASH_CMD="$(which bash 2>/dev/null)"; \
+  [ -n "$BASH_CMD" ] && sed -i 's|root:x:.*|root:x:0:0:root:/root:'$BASH_CMD'|g' "/etc/passwd" || true; \
+  [ -x "$BASH_CMD" ] && [ "$SH_CMD" != "/bin/sh" ] && { rm -Rf "$SH_CMD";ln -s "$BASH_CMD" "$SH_CMD"; } || true; \
+  [ -x "$BASH_CMD" ] && [ ! -L "/bin/sh" ] && { rm -rf "/bin/sh" || true; } && ln -sf "$BASH_CMD" "/bin/sh" || true
 
 ENV SHELL="/bin/bash"
 SHELL [ "/bin/bash", "-c" ]