image-builder: remove unneeded systemd units and files

Remove systemd units and files that are not needed in Kata Containers.
Removing this files we can improve the boot time.

fixes kata-containers#289

Signed-off-by: Julio Montes <julio.montes@intel.com>

image-builder/Dockerfile

@@ -7,4 +7,4 @@ From fedora:latest
 
 RUN [ -n "$http_proxy" ] && sed -i '$ a proxy='$http_proxy /etc/dnf/dnf.conf ; true
 
-RUN dnf install -y qemu-img parted gdisk e2fsprogs gcc xfsprogs
+RUN dnf install -y qemu-img parted gdisk e2fsprogs gcc xfsprogs findutils

image-builder/image_builder.sh

@@ -34,6 +34,29 @@ readonly dax_header_sz=2
 # [2] - https://nvdimm.wiki.kernel.org/2mib_fs_dax
 readonly dax_alignment=2
 
+# The list of systemd units and files that are not needed in Kata Containers
+readonly -a systemd_units=(
+	"systemd-journald"
+	"systemd-journal-flush"
+	"systemd-journald-dev-log"
+	"systemd-udevd"
+	"systemd-udev-trigger"
+	"systemd-udevd-kernel"
+	"systemd-udevd-control"
+	"systemd-timesyncd"
+	"systemd-update-utmp"
+	"systemd-tmpfiles-setup"
+	"systemd-tmpfiles-cleanup"
+	"tmp"
+	"systemd-random-seed"
+	"systemd-coredump@"
+	"systemd-random-seed"
+	"systemd-fstab-generator"
+	"systemd-gpt-auto-generator"
+	"systemd-getty-generator"
+	"systemd-bless-boot-generator"
+)
+
 # Set a default value
 AGENT_INIT=${AGENT_INIT:-no}
 
@@ -344,6 +367,11 @@ create_rootfs_image() {
 	sync
 	OK "rootfs copied"
 
+	info "Removing unneeded systemd units"
+	for u in "${systemd_units[@]}"; do
+		find "${mount_dir}" -type f \( -name "${u}.service" -o -name "${u}.socket" -o -name "${u}.mount" -o -name "${u}.timer" -o -name "${u}" \) -exec rm -f {} \;
+	done
+
 	info "Unmounting root partition"
 	umount "${mount_dir}"
 	OK "Root partition unmounted"