Reducing the number of layers and commands (kubernetes-sigs#9822)

Dockerfile

@@ -1,29 +1,25 @@
 # Use imutable image tags rather than mutable tags (like ubuntu:20.04)
 FROM ubuntu:focal-20220531
-
-ARG ARCH=amd64
-ARG TZ=Etc/UTC
-RUN ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone \
-    && apt update \
-    && apt install -y --no-install-recommends \
-    curl python3 python3-pip sshpass vim \
-    && rm -rf /var/lib/apt/lists/*
-
 # Some tools like yamllint need this
 # Pip needs this as well at the moment to install ansible
 # (and potentially other packages)
 # See: https://github.com/pypa/pip/issues/10219
-ENV LANG=C.UTF-8
+ENV LANG=C.UTF-8 \
+    DEBIAN_FRONTEND=noninteractive
+ARG ARCH=amd64
 
 WORKDIR /kubespray
-COPY *yml /kubespray/
-COPY roles /kubespray/roles
-COPY contrib /kubespray/contrib
-COPY inventory /kubespray/inventory
-COPY library /kubespray/library
-COPY extra_playbooks /kubespray/extra_playbooks
+COPY *yml .
+COPY roles ./roles
+COPY contrib ./contrib
+COPY inventory ./inventory
+COPY library ./library
+COPY extra_playbooks ./extra_playbooks
 
-RUN python3 -m pip install --no-cache-dir \
+RUN apt update && apt install -y --no-install-recommends \
+    curl python3 python3-pip sshpass vim \
+    && rm -rf /var/lib/apt/lists/* /var/log/* \
+    && pip install --no-cache-dir \
     ansible==5.7.1 \
     ansible-core==2.12.5 \
     cryptography==3.4.8 \
@@ -34,6 +30,5 @@ RUN python3 -m pip install --no-cache-dir \
     ruamel.yaml==0.17.21 \
     && find / -type d -name '*__pycache__' -prune -exec rm -rf {} \; \
     && KUBE_VERSION=$(sed -n 's/^kube_version: //p' roles/kubespray-defaults/defaults/main.yaml) \
-    && curl -LO https://storage.googleapis.com/kubernetes-release/release/$KUBE_VERSION/bin/linux/$ARCH/kubectl \
-    && chmod a+x kubectl \
-    && mv kubectl /usr/local/bin/kubectl
+    && curl -L https://storage.googleapis.com/kubernetes-release/release/$KUBE_VERSION/bin/linux/$ARCH/kubectl -o /usr/local/bin/kubectl \
+    && chmod a+x /usr/local/bin/kubectl