image: Require systemd

Building an image requires systemd to be installed in the rootfs as the
init daemon, so assert that systemd is available.

Updated tests so that alpine is only tested as an initrd (it cannot be
an image as it doesn't use systemd).

Added warning note about alpine to the docs.

Fixes #98.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

image-builder/README.md

@@ -16,6 +16,9 @@ $ sudo ./image_builder.sh path/to/rootfs
 
 Where `path/to/rootfs` is the directory populated by `rootfs.sh`.
 
+> **Note**: If you are building an image from an Alpine rootfs, see
+> the important note [here](rootfs-builder/README.md#rootfs-requirements).
+
 ## Further information
 
 For more information about usage (including how to adjust the size of the

image-builder/image_builder.sh

@@ -117,6 +117,15 @@ init_path="/sbin/init"
 init="${ROOTFS}${init_path}"
 [ -x "${init}" ] || [ -L ${init} ] || die "${init_path} is not installed in ${ROOTFS}"
 OK "init is installed"
+
+if [ "${AGENT_INIT}" == "no" ]
+then
+	systemd_path="/lib/systemd/systemd"
+	systemd="${ROOTFS}${systemd_path}"
+	[ -x "${systemd}" ] || [ -L ${systemd} ] || die "${systemd_path} is not installed in ${ROOTFS}"
+	OK "init is systemd"
+fi
+
 [ "${AGENT_INIT}" == "yes" ] || [ -x "${ROOTFS}/usr/bin/${AGENT_BIN}" ] || \
 	die "/usr/bin/${AGENT_BIN} is not installed in ${ROOTFS}
 	use AGENT_BIN env variable to change the expected agent binary name"

rootfs-builder/README.md

@@ -41,6 +41,9 @@ The rootfs must provide at least the following components:
 
 When the `AGENT_INIT` environment variable is set to `yes`, use Kata agent as `/sbin/init`.
 
+> **Note**: `AGENT_INIT=yes` **must** be used for the Alpine distribution
+> since it does not use `systemd` as its init daemon.
+
 ## Creating a rootfs
 
 To build a rootfs for your chosen distribution, run:

tests/image_creation.bats

@@ -48,22 +48,26 @@ function build_initrd()
 function build_rootfs_image_initrd()
 {
 	distro="$1"
+	image="$2"
+	initrd="$3"
+
 	[ -n "$distro" ]
 	build_rootfs $distro
-	build_image
-	build_initrd
+
+	[ "$image" = "yes" ] && build_image
+	[ "$initrd" = "yes" ] && build_initrd
 }
 
 @test "Can create fedora image" {
-	build_rootfs_image_initrd fedora
+	build_rootfs_image_initrd fedora yes yes
 }
 
 @test "Can create clearlinux image" {
-	build_rootfs_image_initrd clearlinux
+	build_rootfs_image_initrd clearlinux yes yes
 }
 
 @test "Can create centos image" {
-	build_rootfs_image_initrd centos
+	build_rootfs_image_initrd centos yes yes
 }
 
 @test "Can create euleros image" {
@@ -71,9 +75,9 @@ function build_rootfs_image_initrd()
 	then
 		skip "travis timeout, see: https://github.com/kata-containers/osbuilder/issues/46"
 	fi
-	build_rootfs_image_initrd euleros
+	build_rootfs_image_initrd euleros yes yes
 }
 
 @test "Can create alpine image" {
-	build_rootfs_image_initrd alpine
+	build_rootfs_image_initrd alpine no yes
 }