diff --git a/spring-postgres/backend/Dockerfile b/spring-postgres/backend/Dockerfile
index 9ab1943..fb6bb86 100755
--- a/spring-postgres/backend/Dockerfile
+++ b/spring-postgres/backend/Dockerfile
@@ -9,16 +9,13 @@ COPY src /workdir/server/src
 RUN mvn install
 
 FROM builder AS dev-envs
-RUN <<EOF
-apt-get update
-apt-get install -y --no-install-recommends git
-EOF
-
-RUN <<EOF
-useradd -s /bin/bash -m vscode
-groupadd docker
+RUN apt update && \
+apt install -y --no-install-recommends git
+
+RUN useradd -s /bin/bash -m vscode && \
+groupadd docker && \
 usermod -aG docker vscode
-EOF
+
 # install Docker tools (cli, buildx, compose)
 COPY --from=gloursdocker/docker / /
 CMD ["mvn", "spring-boot:run"]