make_ext4fs 文件权限控制
16lz
2021-01-26
问题
最近在给 android 系统的 data 分区制作 ext4 镜像，但是发现系统启动后，文件的 user 和 group 都变成了 root，不是原有的属性。困扰了很久。
解决
make_ext4fs 有一个选项是 ‘-a’ ，即挂载点。这个选项是配合android/system/core/include/private/android_filesystem_config.h 用的，根据挂载点修改镜像中文件和目录的权限，比如：
static struct fs_path_config android_dirs[] = { { 00770, AID_SYSTEM, AID_CACHE, "cache" }, { 00771, AID_SYSTEM, AID_SYSTEM, "data/app" }, { 00771, AID_SYSTEM, AID_SYSTEM, "data/app-private" }, { 00771, AID_SYSTEM, AID_SYSTEM, "data/dalvik-cache" }, { 00771, AID_SYSTEM, AID_SYSTEM, "data/data" }, { 00771, AID_SHELL, AID_SHELL, "data/local/tmp" }, { 00771, AID_SHELL, AID_SHELL, "data/local" }, { 01771, AID_SYSTEM, AID_MISC, "data/misc" }, { 00770, AID_DHCP, AID_DHCP, "data/misc/dhcp" }, { 00775, AID_MEDIA_RW, AID_MEDIA_RW, "data/media" }, { 00775, AID_MEDIA_RW, AID_MEDIA_RW, "data/media/Music" }, { 00771, AID_SYSTEM, AID_SYSTEM, "data" }, { 00750, AID_ROOT, AID_SHELL, "sbin" }, { 00755, AID_ROOT, AID_SHELL, "system/bin" }, { 00755, AID_ROOT, AID_SHELL, "system/vendor" }, { 00755, AID_ROOT, AID_SHELL, "system/xbin" }, { 00755, AID_ROOT, AID_ROOT, "system/etc/ppp" }, { 00777, AID_ROOT, AID_ROOT, "sdcard" }, { 00755, AID_ROOT, AID_ROOT, 0 },};
那么，解决方法就有了：去掉 ‘-a’ 选项。
修改文件：android/build/core/Makefile
define build-userdataimage-target $(call pretty,"Target userdata fs image: $(INSTALLED_USERDATAIMAGE_TARGET)") @mkdir -p $(TARGET_OUT_DATA) $(call build-userimage-ext-target,$(TARGET_OUT_DATA),$(INSTALLED_USERDATAIMAGE_TARGET),data,$(INTERNAL_USERIMAGES_EXT_VARIANT),$(BOARD_USERDATAIMAGE_PARTITION_SIZE)) $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE),yaffs)endef
改为：
define build-userdataimage-target $(call pretty,"Target userdata fs image: $(INSTALLED_USERDATAIMAGE_TARGET)") @mkdir -p $(TARGET_OUT_DATA) make_ext4fs -s -l $(BOARD_USERDATAIMAGE_PARTITION_SIZE) $(INSTALLED_USERDATAIMAGE_TARGET) $(TARGET_OUT_DATA) $(hide) $(call assert-max-image-size,$(INSTALLED_USERDATAIMAGE_TARGET),$(BOARD_USERDATAIMAGE_PARTITION_SIZE),yaffs)endef
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