kernels: Add script to convert CentOS kernels

We only convert CentOS 7 kernels for now. CentOS 6 is too
old for most of our purposes.

Signed-off-by: Rolf Neugebauer <rolf.neugebauer@docker.com>

scripts/kernels/Dockerfile.rpm

@@ -0,0 +1,25 @@
+FROM alpine:3.5 AS extract
+
+ARG RPM_URLS
+
+RUN apk add --no-cache curl rpm tar && true
+WORKDIR /rpm
+RUN mkdir extract
+RUN for url in ${RPM_URLS}; do \
+        echo "Extracting: $url"; \
+        curl -fsSL -o dl.rpm $url && \
+        rpm2cpio dl.rpm | cpio -idm ;\
+    done
+
+RUN mkdir /out
+RUN cp -a boot/vmlinuz-* /out/kernel
+RUN cp -a boot/config-* /out/kernel_config
+RUN cp -a boot/System.map-* /out/System.map
+RUN tar cf /out/kernel.tar lib
+RUN tar cf /out/kernel-dev.tar usr || true
+
+FROM linuxkit/toybox-media:d7e82a7d19ccc84c9071fa7a88ecaa58ae958f7c@sha256:4c7d25f2be2429cd08417c36e04161cb924e46f3e419ee33a0aa9ff3a0942e02
+WORKDIR /
+ENTRYPOINT []
+CMD []
+COPY --from=extract /out/* /

scripts/kernels/centos.sh

@@ -0,0 +1,44 @@
+#! /bin/sh
+
+REPO="linuxkit/kernel-centos"
+BASE_URL=http://mirror.centos.org/centos/
+
+TAGS=$(curl --silent -f -lSL https://registry.hub.docker.com/v1/repositories/${REPO}/tags)
+
+LINKS=$(curl -s ${BASE_URL}/ | sed -n 's/.*href="\([^"]*\).*/\1/p')
+# Just get names for Centos 7
+RELEASES=$(echo $LINKS | grep -o "7\.[^ ]*")
+RELEASES="7/ $RELEASES"
+
+# Add updates
+URLS=""
+for RELEASE in $RELEASES; do
+    URLS="$URLS ${BASE_URL}/${RELEASE}/os/x86_64/Packages/"
+done
+URLS="$URLS ${BASE_URL}/7/updates/x86_64/Packages/"
+
+for URL in $URLS; do
+    PACKAGES=$(curl -s ${URL}/ | sed -n 's/.*href="\([^"]*\).*/\1/p')
+
+    KERNEL_RPMS=$(echo $PACKAGES | \
+        grep -o "kernel-[0-9]\+\.[0-9]\+\.[0-9]\+-[0-9]\+\.[^ ]\+\.rpm")
+    for KERNEL_RPM in $KERNEL_RPMS; do
+        RPM_URLS="${URL}/${KERNEL_RPM}"
+
+        VERSION=$(echo $KERNEL_RPM | \
+                      grep -o "[0-9]\+\.[0-9]\+\.[0-9]\+-[0-9\.]\+\.el[0-9]\+")
+
+        if echo $TAGS | grep -q "\"${VERSION}\""; then
+            echo "${REPO}:${VERSION} exists"
+            continue
+        fi
+
+        # Don't pull in the headers. This is mostly for testing
+        # HEADERS_RPM="kernel-headers-${VERSION}.x86_64.rpm"
+        # RPM_URLS="${RPM_URLS} ${URL}/${HEADERS_RPM}"
+
+        docker build -t ${REPO}:${VERSION} -f Dockerfile.rpm --no-cache \
+               --build-arg RPM_URLS="${RPM_URLS}" . &&
+            DOCKER_CONTENT_TRUST=1 docker push ${REPO}:${VERSION}
+    done
+done