[PATCH] cdrom: Compress file system image using Zstandard

[Michael Tremer <michael.tremer@ipfire.org>]

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This patch uses the new Zstandard algorithm to compress the file system
image on the ISO image. This comes with these advantages:

* Compression is about twice as fast than XZ with the parameters we have
  selected here
* We use a lot less memory during compression and can therefore utilise
  all processor cores of the build machines
* Decompression (when installing IPFire and when creating the
  flash-image) is substantically faster

The downside is that the generated ISO image is slighty larger (~10MiB)
which I am okay with as a trade-off for the points mentioned above.

Signed-off-by: Michael Tremer <michael.tremer(a)ipfire.org>
---
 lfs/Config                                  | 5 +++++
 lfs/cdrom                                   | 2 +-
 lfs/flash-images                            | 2 +-
 src/installer/dracut-module/module-setup.sh | 2 +-
 src/installer/main.c                        | 2 +-
 5 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/lfs/Config b/lfs/Config
index f0139e1c5..a2d3cddc5 100644
--- a/lfs/Config
+++ b/lfs/Config
@@ -81,6 +81,11 @@ TAR_OPTIONS = \
 	--acls \
 	--xattrs --xattrs-include='*'
 
+ZSTD_OPTIONS = \
+	-T$(PARALLELISM) \
+	-19 \
+	--long
+
 # URLs that are common sources of downloads.  If you're having trouble with
 # a site you should change its URL to that of a suitable mirror site.
 #
diff --git a/lfs/cdrom b/lfs/cdrom
index c58fc0885..18c63c79b 100644
--- a/lfs/cdrom
+++ b/lfs/cdrom
@@ -165,7 +165,7 @@ $(TARGET) : $(patsubst %,$(DIR_DL)/%,$(objects))
 		-C / --files-from=$(DIR_TMP)/ROOTFILES | tar $(TAR_OPTIONS) -x -C $(DIR_TMP)/root
 	rm -f $(DIR_TMP)/ROOTFILES
 	mkdir $(DIR_TMP)/root/sys
-	cd $(DIR_TMP)/root && tar $(TAR_OPTIONS) -cf - * | xz $(XZ_OPT) > $(DIR_TMP)/cdrom/distro.img
+	cd $(DIR_TMP)/root && tar $(TAR_OPTIONS) -cf - * | zstd $(ZSTD_OPTIONS) > $(DIR_TMP)/cdrom/distro.img
 	rm -rf $(DIR_TMP)/root
 
 	# Other files
diff --git a/lfs/flash-images b/lfs/flash-images
index 15398d051..72e635073 100644
--- a/lfs/flash-images
+++ b/lfs/flash-images
@@ -152,7 +152,7 @@ endif
 
 	# Install IPFire
 ifneq "$(BUILD_PLATFORM)" "arm"
-	tar $(TAR_OPTIONS) -x --xz -C $(MNThdd)/ -f $(DIR_TMP)/cdrom/distro.img
+	tar $(TAR_OPTIONS) -x --zstd -C $(MNThdd)/ -f $(DIR_TMP)/cdrom/distro.img
 else
 	tar $(TAR_OPTIONS) -x -C $(MNThdd)/ -f $(DIR_TMP)/cdrom/distro.img
 endif
diff --git a/src/installer/dracut-module/module-setup.sh b/src/installer/dracut-module/module-setup.sh
index ef4b15bdc..29ec4c0d7 100755
--- a/src/installer/dracut-module/module-setup.sh
+++ b/src/installer/dracut-module/module-setup.sh
@@ -33,7 +33,7 @@ install() {
     instmods ext4 iso9660 reiserfs vfat xfs
 
     # Extraction
-    inst_multiple tar gzip lzma xz
+    inst_multiple tar gzip zstd
 
     # Networking
     inst_multiple dhcpcd ethtool hostname ip ping sort wget
diff --git a/src/installer/main.c b/src/installer/main.c
index 00d172888..7a172e4ae 100644
--- a/src/installer/main.c
+++ b/src/installer/main.c
@@ -781,7 +781,7 @@ int main(int argc, char *argv[]) {
 
 	// Extract files...
 	snprintf(commandstring, STRING_SIZE,
-		"/bin/tar --acls --xattrs --xattrs-include='*' -C /harddisk -xvf /cdrom/distro.img --xz 2>/dev/null");
+		"/bin/tar --acls --xattrs --xattrs-include='*' -C /harddisk -xvf /cdrom/distro.img --zstd 2>/dev/null");
 
 	if (runcommandwithprogress(60, 4, title, commandstring, INST_FILECOUNT,
 			_("Installing the system..."), logfile)) {
-- 
2.20.1