osbuilder: add dracut build method

Add the option to build image and initrd using dracut.

Fixes: #311

Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Marco Vedovati <mvedovati@suse.com>

Makefile

@@ -9,15 +9,17 @@ ROOTFS_BUILDER := $(MK_DIR)/rootfs-builder/rootfs.sh
 INITRD_BUILDER := $(MK_DIR)/initrd-builder/initrd_builder.sh
 IMAGE_BUILDER  := $(MK_DIR)/image-builder/image_builder.sh
 
+DISTRO                := centos
+BUILD_METHOD          := distro
+BUILD_METHOD_LIST     := distro dracut
 AGENT_INIT            ?= no
-DISTRO                ?= centos
+ROOTFS_BUILD_DEST     := $(shell pwd)
-ROOTFS_BUILD_DEST     := $(PWD)
+IMAGES_BUILD_DEST     := $(shell pwd)
-IMAGES_BUILD_DEST     := $(PWD)
-DISTRO_ROOTFS         := $(ROOTFS_BUILD_DEST)/$(DISTRO)_rootfs
 ROOTFS_MARKER_SUFFIX   := _rootfs.done
-DISTRO_ROOTFS_MARKER  := $(ROOTFS_BUILD_DEST)/.$(DISTRO)$(ROOTFS_MARKER_SUFFIX)
+TARGET_ROOTFS         := $(ROOTFS_BUILD_DEST)/$(DISTRO)_rootfs
-DISTRO_IMAGE          := $(IMAGES_BUILD_DEST)/kata-containers.img
+TARGET_ROOTFS_MARKER  := $(ROOTFS_BUILD_DEST)/.$(DISTRO)$(ROOTFS_MARKER_SUFFIX)
-DISTRO_INITRD         := $(IMAGES_BUILD_DEST)/kata-containers-initrd.img
+TARGET_IMAGE          := $(IMAGES_BUILD_DEST)/kata-containers.img
+TARGET_INITRD         := $(IMAGES_BUILD_DEST)/kata-containers-initrd.img
 
 VERSION_FILE   := ./VERSION
 VERSION        := $(shell grep -v ^\# $(VERSION_FILE))
@@ -25,6 +27,34 @@ COMMIT_NO      := $(shell git rev-parse HEAD 2> /dev/null || true)
 COMMIT         := $(if $(shell git status --porcelain --untracked-files=no),${COMMIT_NO}-dirty,${COMMIT_NO})
 VERSION_COMMIT := $(if $(COMMIT),$(VERSION)-$(COMMIT),$(VERSION))
 
+ifeq ($(filter $(BUILD_METHOD),$(BUILD_METHOD_LIST)),)
+    $(error Invalid BUILD_METHOD value '$(BUILD_METHOD)'. Supported values: $(BUILD_METHOD_LIST))
+endif
+
+ifeq (dracut,$(BUILD_METHOD))
+  DISTRO                :=
+  TARGET_ROOTFS         := dracut_rootfs
+  TARGET_ROOTFS_MARKER  := $(ROOTFS_BUILD_DEST)/.dracut$(ROOTFS_MARKER_SUFFIX)
+  # dracut specific variables
+  DRACUT_KVERSION    :=
+  DRACUT_OVERLAY_DIR := $(MK_DIR)/dracut_overlay
+  DRACUT_DIR         := $(MK_DIR)/dracut
+  DRACUT_CONF_DIR    := $(DRACUT_DIR)/dracut.conf.d
+  DRACUT_OPTIONS     := --no-compress --conf /dev/null --confdir $(DRACUT_CONF_DIR)
+
+  ifneq (,$(DRACUT_KVERSION))
+    # If a kernel version is not specified, do not make systemd load modules
+    # at startup
+    DRACUT_KMODULES  := $(shell grep "^drivers=" $(DRACUT_CONF_DIR)/10-drivers.conf | sed -E "s,^drivers=\"(.*)\"$$,\1,")
+  else
+    DRACUT_OPTIONS += --no-kernel
+  endif
+
+  ifeq (,$(DRACUT_OVERLAY_DIR))
+    $(error DRACUT_OVERLAY_DIR cannot be empty)
+  endif
+endif
+
 # Set the variable to silent logs using chronic
 OSBUILDER_USE_CHRONIC :=
 
@@ -53,7 +83,17 @@ rootfs-%: $(ROOTFS_BUILD_DEST)/.%$(ROOTFS_MARKER_SUFFIX)
 .PRECIOUS: $(ROOTFS_BUILD_DEST)/.%$(ROOTFS_MARKER_SUFFIX)
 $(ROOTFS_BUILD_DEST)/.%$(ROOTFS_MARKER_SUFFIX):: rootfs-builder/%
 	$(call silent_run,Creating rootfs for "$*",$(ROOTFS_BUILDER) -o $(VERSION_COMMIT) -r $(ROOTFS_BUILD_DEST)/$*_rootfs $*)
-	touch $@
+	@touch $@
+
+# To generate a dracut rootfs, we first generate a dracut initrd and then
+# extract it in a local folder.
+# Notes:
+# - assuming a not compressed initrd.
+.PRECIOUS: $(ROOTFS_BUILD_DEST)/.dracut$(ROOTFS_MARKER_SUFFIX)
+$(ROOTFS_BUILD_DEST)/.dracut$(ROOTFS_MARKER_SUFFIX): $(TARGET_INITRD)
+	mkdir -p $(TARGET_ROOTFS)
+	cat $< | cpio --extract --preserve-modification-time --make-directories --directory=$(TARGET_ROOTFS)
+	@touch $@
 
 image-%: $(IMAGES_BUILD_DEST)/kata-containers-image-%.img
 	@ # DONT remove. This is not cancellation rule.
@@ -73,19 +113,37 @@ $(IMAGES_BUILD_DEST)/kata-containers-initrd-%.img: rootfs-%
 all: image initrd
 
 .PHONY: rootfs
-rootfs: $(DISTRO_ROOTFS_MARKER)
+rootfs: $(TARGET_ROOTFS_MARKER)
 
 .PHONY: image
-image: $(DISTRO_IMAGE)
+image: $(TARGET_IMAGE)
+
+$(TARGET_IMAGE): $(TARGET_ROOTFS_MARKER)
+	$(call silent_run,Creating image based on "$(TARGET_ROOTFS)",$(IMAGE_BUILDER) -o $@ "$(TARGET_ROOTFS)")
 
-$(DISTRO_IMAGE): $(DISTRO_ROOTFS_MARKER)
-	$(call silent_run,Creating image based on "$(DISTRO_ROOTFS)",$(IMAGE_BUILDER) "$(DISTRO_ROOTFS)")
 
 .PHONY: initrd
-initrd: $(DISTRO_INITRD)
+initrd: $(TARGET_INITRD)
 
-$(DISTRO_INITRD): $(DISTRO_ROOTFS_MARKER)
+ifeq (distro,$(BUILD_METHOD))
-	$(call silent_run,Creating initrd image based on "$(DISTRO_ROOTFS)",$(INITRD_BUILDER) "$(DISTRO_ROOTFS)")
+$(TARGET_INITRD): $(TARGET_ROOTFS_MARKER)
+	$(call silent_run,Creating initrd image based on "$(TARGET_ROOTFS)",$(INITRD_BUILDER) "$(TARGET_ROOTFS)")
+else
+$(TARGET_INITRD): $(DRACUT_OVERLAY_DIR)
+	@echo Creating initrd image based on the host OS using dracut
+	dracut $(DRACUT_OPTIONS) --include $< / $@ $(DRACUT_KVERSION)
+endif
+
+# Notes on overlay dir:
+# - If user specified any kernel module in the dracut conf file,
+#   we need to make sure these are pre-loaded at startup using
+#   systemd modules-load.d
+$(DRACUT_OVERLAY_DIR):
+	mkdir -p $@
+	# Modules preload
+	$(ROOTFS_BUILDER) -o $(VERSION_COMMIT) -r $@
+	mkdir -p $@/etc/modules-load.d
+	echo $(DRACUT_KMODULES) | tr " " "\n" > $@/etc/modules-load.d/kata-modules.conf
 
 .PHONY: test
 test:
@@ -140,7 +198,7 @@ install-scripts:
 
 .PHONY: clean
 clean:
-	rm -rf $(DISTRO_ROOTFS_MARKER) $(DISTRO_ROOTFS) $(DISTRO_IMAGE) $(DISTRO_INITRD)
+	rm -rf $(TARGET_ROOTFS_MARKER) $(TARGET_ROOTFS) $(TARGET_IMAGE) $(TARGET_INITRD) $(DRACUT_OVERLAY_DIR)
 
 # Prints the name of the variable passed as suffix to the print- target,
 # E.g., if Makefile contains:

README.md

@@ -2,18 +2,25 @@
 
 # osbuilder
 
-* [Introduction](#introduction)
+* [osbuilder](#osbuilder)
-* [Terms](#terms)
+  * [Introduction](#introduction)
-* [Usage](#usage)
+  * [Terms](#terms)
+  * [Building](#building)
      * [Rootfs creation](#rootfs-creation)
         * [Rootfs with systemd as init](#rootfs-with-systemd-as-init)
         * [Rootfs with the agent as init](#rootfs-with-the-agent-as-init)
+        * [dracut based rootfs](#dracut-based-rootfs)
      * [Image creation](#image-creation)
         * [Image with systemd as init](#image-with-systemd-as-init)
         * [Image with the agent as init](#image-with-the-agent-as-init)
+        * [dracut based image](#dracut-based-image)
      * [Initrd creation](#initrd-creation)
-    * [Tests](#tests)
+        * [Rootfs based initrd](#rootfs-based-initrd)
-* [Platform-Distro Compatibility Matrix](#platform-distro-compatibility-matrix)
+        * [dracut based initrd](#dracut-based-initrd)
+     * [dracut options](#dracut-options)
+        * [Add kernel modules](#add-kernel-modules)
+  * [Testing](#testing)
+  * [Platform-Distro Compatibility Matrix](#platform-distro-compatibility-matrix)
 
 ## Introduction
 
@@ -53,16 +60,39 @@ This section describes the terms used for all documentation in this repository.
 
   A particular version of a Linux distribution used to create a rootfs from.
 
-## Usage
+- dracut
+
+  A guest OS build method where the building host is used as the Base OS.
+  For more information refer to the [dracut homepage](https://dracut.wiki.kernel.org/index.php/Main_Page).
+
+## Building
 
 The top-level `Makefile` contains an example of how to use the available components.
 
-By default, components will run on the host system. However, some components
+Two build methods are available, `distro` and `dracut`.
+By default, the `distro` build method is used, and this creates a rootfs using
+distro specific commands (e.g.: `debootstrap` for Debian or `yum` for CentOS).
+The `dracut` build method uses the distro-agnostic tool `dracut` to obtain the same goal.
+
+By default components are run on the host system. However, some components
 offer the ability to run from within Docker (for ease of setup) by setting the
 `USE_DOCKER=true` variable.
 
 For more detailed information, consult the documentation for a particular component.
 
+When invoking the appropriate make target as showed below, a single command is used
+to generate an initrd or an image. This is what happens in details:
+1. A rootfs is generated based on the specified target distribution.
+2. The rootfs is provisioned with Kata-specific components and configuration files.
+3. The rootfs is used as a base to generate an initrd or an image.
+
+When using the dracut build method however, the build sequence is different:
+1. An overlay directory is populated with Kata-specific components.
+2. dracut is instructed to merge the overlay directory with the required host-side
+filesystem components to generate an initrd.
+3. When generating an image, the initrd is extracted to obtain the base rootfs for
+the image.
+
 ### Rootfs creation
 
 This section shows how to build a basic rootfs using the default distribution.
@@ -81,6 +111,15 @@ $ sudo -E PATH=$PATH make USE_DOCKER=true rootfs
 $ sudo -E PATH=$PATH make USE_DOCKER=true AGENT_INIT=yes rootfs
 ```
 
+#### dracut based rootfs
+
+> **Note**: the dracut build method does not need a rootfs as a base for an image or initrd.
+However, a rootfs can be generated by extracting the generated initrd.
+
+```
+$ sudo -E PATH=$PATH make BUILD_METHOD=dracut rootfs
+```
+
 ### Image creation
 
 This section shows how to create an image from the already-created rootfs. For
@@ -99,18 +138,55 @@ $ sudo -E PATH=$PATH make USE_DOCKER=true image
 $ sudo -E PATH=$PATH make USE_DOCKER=true AGENT_INIT=yes image
 ```
 
+#### dracut based image
+
+> Note: the dracut build method generates an image by first building an initrd,
+and then using the rootfs extracted from it.
+
+```
+$ sudo -E PATH=$PATH make BUILD_METHOD=dracut image
+```
+
 ### Initrd creation
 
-To create an initrd from the already-created rootfs with the agent acting as the init daemon:
+#### Rootfs based initrd
+
+Create an initrd from the already-created rootfs and with the agent acting as the init daemon
+using:
 
 ```
 $ sudo -E PATH=$PATH make AGENT_INIT=yes initrd
 ```
 
+#### dracut based initrd
+
+Create an initrd using the dracut build method with:
+
+```
+$ sudo -E PATH=$PATH make BUILD_METHOD=dracut AGENT_INIT=yes initrd
+```
+
 For further details,
 see [the initrd builder documentation](initrd-builder/README.md).
 
-### Tests
+### dracut options
+
+#### Add kernel modules
+
+If the initrd or image needs to contain kernel modules, this can be done by:
+
+1. Specify the name of the modules (as reported by `modinfo MODULE-NAME`) in
+`dracut/dracut.conf.d/10-drivers.conf`. For example this file can contain:
+```
+drivers="9p 9pnet 9pnet_virtio"
+```
+2. Set the `DRACUT_KVERSION` make variable to the release name of the kernel that
+is paired with the built image or initrd, using the `uname -r` format. For example:
+```
+$ make BUILD_METHOD=dracut DRACUT_KVERSION=5.2.1-23-kata AGENT_INIT=yes initrd
+```
+
+## Testing
 
 ```
 $ make test
@@ -120,6 +196,12 @@ For further details, see [the tests documentation](tests/README.md).
 
 ## Platform-Distro Compatibility Matrix
 
+The following table illustrates what target architecture is supported for each
+of the the osbuilder distributions.
+
+> Note: this table is not relevant for the dracut build method, since it supports
+any Linux distribution and architecture where dracut is available.
+
 |           |Alpine            |CentOS            |Clear Linux       |Debian/Ubuntu     |EulerOS           |Fedora            |openSUSE          |
 |--         |--                |--                |--                |--                |--                |--                |--                |
 |**ARM64**  |:heavy_check_mark:|:heavy_check_mark:|                  |                  |:heavy_check_mark:|:heavy_check_mark:|:heavy_check_mark:|

dracut/dracut.conf.d/00-base.conf

@@ -0,0 +1,17 @@
+#
+# Copyright (c) 2019 SUSE LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# Main dracut config for Kata Containers
+
+# do NOT combine early microcode with ramdisk
+early_microcode="no"
+# do NOT install only what's needed to boot the local host 
+hostonly="no"
+# do NOT store the kernel command line arguments in the initramfs
+hostonly_cmdline="no"
+# create reproducible images
+reproducible="yes"
+# dracut modules to include (NOTE: these are NOT kernel modules)
+dracutmodules="kernel-modules udev-rules syslog systemd"

dracut/dracut.conf.d/10-drivers.conf

@@ -0,0 +1,9 @@
+#
+# Copyright (c) 2019 SUSE LLC
+#
+# SPDX-License-Identifier: Apache-2.0
+
+# Specify a space-separated set of kernel modules to copy from the host to 
+# the initramfs image. For example:
+# drivers="9p 9pnet 9pnet_virtio"
+drivers=""

rootfs-builder/README.md

@@ -11,7 +11,7 @@
      * [Create template files](#create-template-files)
      * [Modify template files](#modify-template-files)
      * [Expected rootfs directory content](#expected-rootfs-directory-content)
-     * [Optional - Customise the rootfs](#optional---customise-the-rootfs)
+     * [Optional - Customize the rootfs](#optional---customize-the-rootfs)
         * [Adding extra packages](#adding-extra-packages)
         * [Arbitrary rootfs changes](#arbitrary-rootfs-changes)
 
@@ -26,24 +26,24 @@ distribution. The script supports multiple distributions and can be extended
 to add further ones.
 
 ### Extra features
+
 #### Supported distributions list
-Supported distributions can be listed with:
+
+List the supported distributions by running the following:
 ```
 $ ./rootfs.sh -l
 ```
 
 #### Generate Kata specific files
-`rootfs.sh` can be used to only populate a target directory with the set of Kata
+The `rootfs.sh` script can be used to populate a directory with only Kata specific files and
-specific files and components integrable into a generic Linux rootfs to generate
+components, without creating a full usable rootfs.
-a Kata guest OS image.
+This feature is used to create a rootfs based on a distribution not officially
-This feature can be used when creating a rootfs with a distribution not officially
+supported by osbuilder, and when building an image using the dracut build method.
-supported by osbuilder.
-It is also used when building the rootfs using the 'dracut' build method.
 
-To obtain this, simply invoke `rootfs.sh` without specifying a target rootfs, e.g.:
+To achieve this, simply invoke `rootfs.sh` without specifying a target rootfs, e.g.:
 ```
-mkdir kata-overlay
+$ mkdir kata-overlay
-./rootfs.sh -r `pwd`/kata-overlay
+$ ./rootfs.sh -r "$PWD/kata-overlay"
 ```
 
 ## Rootfs requirements
@@ -177,7 +177,7 @@ After the new directory structure is created:
 After the function `build_rootfs` is called, the script expects the
 rootfs directory to contain `/sbin/init` and `/sbin/kata-agent` binaries.
 
-### Optional - Customise the rootfs
+### Optional - Customize the rootfs
 
 For particular use cases developers might want to modify the guest OS.
 

rootfs-builder/rootfs.sh

@@ -386,12 +386,15 @@ build_rootfs_distro()
 # This is used when a distro is not specified.
 prepare_overlay()
 {
-	pushd "${ROOTFS_DIR}" >> /dev/null
+	pushd "${ROOTFS_DIR}" > /dev/null
 	mkdir -p ./etc ./lib/systemd ./sbin ./var
 	ln -sf  ./usr/lib/systemd/systemd ./init
 	ln -sf  ../../init ./lib/systemd/systemd
 	ln -sf  ../init ./sbin/init
-	popd  >> /dev/null
+	# Kata sytemd unit file
+	mkdir -p ./etc/systemd/system/basic.target.wants/
+	ln -sf /usr/lib/systemd/system/kata-containers.target ./etc/systemd/system/basic.target.wants/kata-containers.target
+	popd  > /dev/null
 }
 
 # Setup an existing rootfs directory, based on the OPTIONAL distro name
@@ -405,14 +408,40 @@ setup_rootfs()
 	if [ "$PWD" != "/" ] ; then
 		rm -rf ./var/cache/ ./var/lib ./var/log ./var/tmp
 	fi
+
 	ln -s ../tmp ./var/
 
 	# For some distros tmp.mount may not be installed by default in systemd paths
 	if ! [ -f "./etc/systemd/system/tmp.mount" ] && \
 		! [ -f "./usr/lib/systemd/system/tmp.mount" ] &&
 		[ "$AGENT_INIT" != "yes" ]; then
+		local unitFile="./etc/systemd/system/tmp.mount"
 		info "Install tmp.mount in ./etc/systemd/system"
-		cp ./usr/share/systemd/tmp.mount ./etc/systemd/system/tmp.mount
+		mkdir -p `dirname "$unitFile"`
+		cp ./usr/share/systemd/tmp.mount "$unitFile" || cat > "$unitFile" << EOT
+#  This file is part of systemd.
+#
+#  systemd is free software; you can redistribute it and/or modify it
+#  under the terms of the GNU Lesser General Public License as published by
+#  the Free Software Foundation; either version 2.1 of the License, or
+#  (at your option) any later version.
+
+[Unit]
+Description=Temporary Directory (/tmp)
+Documentation=man:hier(7)
+Documentation=https://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
+ConditionPathIsSymbolicLink=!/tmp
+DefaultDependencies=no
+Conflicts=umount.target
+Before=local-fs.target umount.target
+After=swap.target
+
+[Mount]
+What=tmpfs
+Where=/tmp
+Type=tmpfs
+Options=mode=1777,strictatime,nosuid,nodev
+EOT
 	fi
 
 	popd  >> /dev/null
@@ -486,7 +515,7 @@ parse_arguments()
 			l)	get_distros | sort && exit 0;;
 			o)	OSBUILDER_VERSION="${OPTARG}" ;;
 			r)	ROOTFS_DIR="${OPTARG}" ;;
-			t)	get_test_config "${OPTARG}" && exit -1;;
+			t)	get_test_config "${OPTARG}" && exit 0;;
 			*)  die "Found an invalid option";;
 		esac
 	done