[Buildroot] [PATCH next v5 2/3] fs/cpio: new option to use dracut tool

["Arnout Vandecappelle (Essensium/Mind)" <arnout@mind.be>]

From: Thierry Bultel <thierry.bultel@linatsea.fr>

Adds an option to invoke the dracut host tool, providing
a configuration file, instead of having a full cpio archive
of the whole target directory.

A default configuration file is provided. It assumes busybox init.
ideally, a different default should be used in case of systemd init, but
that's left for future work.

Signed-off-by: Thierry Bultel <thierry.bultel@linatsea.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
---
Changes v1 -> v2 (suggested by Arnout and Yann)
  - was a new fs type, now an option of cpio
  - deals with the case of a build with no kernel
  - gets the kernel name in a smarter way
  - checks for the name of dracut configuration file
Changes v2 -> v3
  - fixed a typo on the --no-kernel option for dracut
  - removed the unneeded dependency to kernel
  - added tests for cpio, for both full, and dracut modes
Changes v3 -> v4
  - Config.in: applied Yann's comments on syntax and option in choice
  - do no export TARGET_CROSS but give it in command line instead
  - use $(ROOTFS_CPIO_DIR) as base for tmp directory
  - let original, full cpio, first in the code, and dracut mode after
  - removed unwanted comment in dracut.conf (in tests)
Changes v4 -> v5 (Arnout)
  - move runtime test to separate patch;
  - fix check-package errors;
  - add default dracut.conf file, the one from the runtime test;
  - remove bash from dracut.conf;
  - remove dependency on busybox or systemd init;
  - add help text to BR2_TARGET_ROOTFS_CPIO_DRACUT_CONF_FILE;
  - use our compression instead of dracut's;
  - still allow uimage;
  - add --sysroot option in dracut call;
  - adapt paths and environment according to changes in previous commit;
  - use : instead of . to separate ifeq conditions;
  - add support for reproducible (shared with cpio);
  - use ROOTFS_CPIO_OPTS instead of ROOTFS_CPIO_DRACUT_CMD_OPTS;
  - remove --keep option, isn't needed.
---
 fs/cpio/Config.in   | 34 +++++++++++++++++
 fs/cpio/cpio.mk     | 33 ++++++++++++++++
 fs/cpio/dracut.conf | 93 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 160 insertions(+)
 create mode 100644 fs/cpio/dracut.conf

diff --git a/fs/cpio/Config.in b/fs/cpio/Config.in
index c1151a2881..de83aaad65 100644
--- a/fs/cpio/Config.in
+++ b/fs/cpio/Config.in
@@ -7,6 +7,40 @@ config BR2_TARGET_ROOTFS_CPIO
 
 if BR2_TARGET_ROOTFS_CPIO
 
+choice
+	prompt "cpio type"
+	default BR2_TARGET_ROOTFS_CPIO_FULL
+
+config BR2_TARGET_ROOTFS_CPIO_FULL
+	bool "cpio the whole root filesystem"
+	help
+	  Build a cpio archive containing the whole the root filesystem.
+
+config BR2_TARGET_ROOTFS_CPIO_DRACUT
+	bool "Invoke dracut to make a partial initramfs"
+	select BR2_PACKAGE_HOST_DRACUT
+	select BR2_PACKAGE_HOST_UBOOT_TOOLS
+	help
+	  Build an additional initramfs using dracut. This only contains
+	  a subset of the rootfs, as determined by the configuration
+	  file.
+	  This can be useful to create a recovery system, for instance.
+
+endchoice
+
+if BR2_TARGET_ROOTFS_CPIO_DRACUT
+config BR2_TARGET_ROOTFS_CPIO_DRACUT_CONF_FILE
+	string "dracut configuration file"
+	default "fs/cpio/dracut.conf"
+	help
+	  Dracut configuration file. It determines which parts of the
+	  rootfs get included in the cpio image. See dracut.conf(5) or
+	  https://github.com/dracutdevs/dracut/blob/master/man/dracut.conf.5.asc
+
+	  The default configuration file is suitable for busybox init.
+	  It doesn't, however, pivot_root into a full rootfs.
+endif
+
 choice
 	prompt "Compression method"
 	default BR2_TARGET_ROOTFS_CPIO_NONE
diff --git a/fs/cpio/cpio.mk b/fs/cpio/cpio.mk
index 81f8c393d1..b62d804ad8 100644
--- a/fs/cpio/cpio.mk
+++ b/fs/cpio/cpio.mk
@@ -36,6 +36,8 @@ ROOTFS_CPIO_DEPENDENCIES += host-cpio
 ROOTFS_CPIO_OPTS += --reproducible
 endif
 
+ifeq ($(BR2_TARGET_ROOTFS_CPIO_FULL),y)
+
 define ROOTFS_CPIO_CMD
 	cd $(TARGET_DIR) && \
 	find . \
@@ -44,6 +46,37 @@ define ROOTFS_CPIO_CMD
 	> $@
 endef
 
+else ifeq ($(BR2_TARGET_ROOTFS_CPIO_DRACUT),y)
+
+ROOTFS_CPIO_DEPENDENCIES += host-dracut
+
+ifeq ($(BR_BUILDING):$(BR2_TARGET_ROOTFS_CPIO_DRACUT_CONF_FILE),y:)
+$(error No dracut config file name specified, check your BR2_TARGET_ROOTFS_CPIO_DRACUT_CONF_FILE setting)
+endif
+
+ifeq ($(BR2_LINUX_KERNEL),y)
+ROOTFS_CPIO_DEPENDENCIES += linux
+ROOTFS_CPIO_OPTS += --kver $(LINUX_VERSION_PROBED)
+else
+ROOTFS_CPIO_OPTS += --no-kernel
+endif
+
+define ROOTFS_CPIO_CMD
+	mkdir -p $(ROOTFS_CPIO_DIR)/tmp
+
+	$(HOST_DIR)/bin/dracut \
+		$(ROOTFS_CPIO_OPTS) \
+		-c $(BR2_TARGET_ROOTFS_CPIO_DRACUT_CONF_FILE) \
+		--sysroot $(TARGET_DIR) \
+		--tmpdir $(ROOTFS_CPIO_DIR)/tmp \
+		-M \
+		--force \
+		--no-compress \
+		$@
+endef
+
+endif #BR2_TARGET_ROOTFS_CPIO_DRACUT
+
 ifeq ($(BR2_TARGET_ROOTFS_CPIO_UIMAGE),y)
 ROOTFS_CPIO_DEPENDENCIES += host-uboot-tools
 define ROOTFS_CPIO_UBOOT_MKIMAGE
diff --git a/fs/cpio/dracut.conf b/fs/cpio/dracut.conf
new file mode 100644
index 0000000000..6184457723
--- /dev/null
+++ b/fs/cpio/dracut.conf
@@ -0,0 +1,93 @@
+#Simple dracut config for a system without systemd
+
+#Dracut configuration
+
+show_modules=yes
+i18n_install_all=no
+lvmconf=no
+mdadmconf=no
+early_microcode=no
+hostonly=no
+hostonly_cmdline=no
+use_fstab=no
+kernel_cmdline="rd.break=initqueue"
+do_strip=no
+
+# Dracut modules needed
+add_dracutmodules+=" \
+busybox-init
+"
+
+# Modules to ignore
+omit_dracutmodules+=" \
+bash \
+biosdevname \
+btrfs \
+bluetooth \
+busybox \
+caps \
+cifs \
+crypt \
+crypt-gpg \
+dash \
+dbus-broker \
+dbus-daemon \
+dm \
+dmraid \
+dmsquash-live-ntfs \
+dracut-systemd \
+fcoe \
+fcoe-uefi \
+fs-lib \
+iscsi \
+i18n \
+lvmmerge \
+lvm \
+lunmask \
+mdraid \
+memstrack \
+mksh \
+modsign \
+mount-root \
+multipath \
+nbd \
+network-legacy \
+network-wicked \
+nfs \
+nvdimm \
+nvmf \
+parse-lunmask \
+qemu \
+qemu-net \
+resume \
+rootfs-block \
+rngd \
+systemd \
+systemd-udevd \
+systemd-coredump \
+systemd-ask-password \
+systemd-timedated \
+systemd-rfkill \
+systemd-resolved \
+systemd-hostnamed \
+systemd-initrd \
+systemd-journald \
+systemd-ldconfig \
+systemd-networkd \
+systemd-timesyncd \
+systemd-veritysetup \
+systemd-modules-load \
+systemd-sysctl \
+systemd-repart \
+systemd-sysext \
+systemd-sysusers \
+systemd-tmpfiles \
+squash \
+ssh-client \
+stratis \
+tpm2-tss \
+udev-rules \
+url-lib \
+usrmount \
+"
+
-- 
2.37.1

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