make snod
在 build/core/Makefile 可以看到 snod 這個 target:
.PHONY: systemimage-nodeps snod
systemimage-nodeps snod: $(filter-out systemimage-nodeps snod,$(MAKECMDGOALS)) \
| $(INTERNAL_MKUSERFS)
@echo "make $@: ignoring dependencies"
$(call build-systemimage-target,$(INSTALLED_SYSTEMIMAGE))
$(hide) $(call assert-max-image-size,$(INSTALLED_SYSTEMIMAGE),$(BOARD_SYSTEMIMAGE_PARTITION_SIZE),yaffs)
有說明是： make system.img ignoring depencies.
至於 做出 system.img 的command，可以用 showcommands 這個 target..
make showcommands snod
這樣 就會 show 出所有 build snod 這個target 的 command:
make snod: ignoring dependencies
Target system fs image: out/target/product/imx51_bbg/system.img
num_blocks=`du -sk out/target/product/imx51_bbg/system | tail -n1 | awk '{print $1;}'`; if [ $num_blocks -lt 20480 ]; then extra_blocks=3072; else extra_blocks=20480; fi ; if [ "" != "" ]; then num_blocks=; num_inodes=4096; else num_blocks=`expr $num_blocks + $extra_blocks` ; num_inodes=`find out/target/product/imx51_bbg/system | wc -l` ; num_inodes=`expr $num_inodes + 500`; fi; out/host/linux-x86/bin/genext2fs -a -d out/target/product/imx51_bbg/system -b $num_blocks -N $num_inodes -m 0 out/target/product/imx51_bbg/system.img;
tune2fs -L system out/target/product/imx51_bbg/system.img
tune2fs 1.41.11 (14-Mar-2010)
tune2fs -j out/target/product/imx51_bbg/system.img
tune2fs 1.41.11 (14-Mar-2010)
Creating journal inode: done
This filesystem will be automatically checked every 20 mounts or
0 days, whichever comes first. Use tune2fs -c or -i to override.
tune2fs -C 1 out/target/product/imx51_bbg/system.img
tune2fs 1.41.11 (14-Mar-2010)
Setting current mount count to 1
e2fsck -fy out/target/product/imx51_bbg/system.img ; [ $? -lt 4 ]
e2fsck 1.41.11 (14-Mar-2010)
Filesystem did not have a UUID; generating one.
Filesystem has feature flag(s) set, but is a revision 0 filesystem. Fix? yes
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
/lost+found not found. Create? yes
Pass 4: Checking reference counts
Pass 5: Checking group summary information
system: ***** FILE SYSTEM WAS MODIFIED *****
system: 596/1144 files (1.8% non-contiguous), 86956/103536 blocks
true
大概是用 genext2fs 從 system folder 做出一個ext2 的 system.img。
然後再用 tune2fs -j 把 system.img 轉為 ext3。
這個 build-userimage-ext2-target 定義在 external/genext2fs/Config.mk
# $(1): src directory
# $(2): output file
# $(3): label (if any)
# $(4): if true, add journal
define build-userimage-ext2-target
@mkdir -p $(dir $(2))
$(hide) num_blocks=`du -sk $(1) | tail -n1 | awk '{print $$1;}'`;\
if [ $$num_blocks -lt 20480 ]; then extra_blocks=3072; \
else extra_blocks=20480; fi ; \
num_blocks=`expr $$num_blocks + $$extra_blocks` ; \
num_inodes=`find $(1) | wc -l` ; num_inodes=`expr $$num_inodes + 500`; \
$(MKEXT2IMG) -a -d $(1) -b $$num_blocks -N $$num_inodes -m 0 $(2)
$(if $(strip $(3)),\
$(hide) $(TUNE2FS) -L $(strip $(3)) $(2))
$(if $(strip $(4)),\
$(hide) $(TUNE2FS) -j $(2))
$(TUNE2FS) -C 1 $(2)
$(E2FSCK) -fy $(2) ; [ $$? -lt 4 ]
endef
是在 core/Makefile include 近來的：
ifeq ($(TARGET_USERIMAGES_USE_EXT2),true)
include external/genext2fs/Config.mk
INTERNAL_MKUSERFS := $(MKEXT2IMG)
..
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