⑴ android mediaserver怎麼啟動
mediaserver 開機的時候就啟動，說具體一點是在initrc裡面啟動的，這裡面還啟動了很多其他的server
⑵ Android怎麼讓安裝的apk通過jni調用腳本時運行在root許可權下
解決方法是在manifest中將AP提升至system許可權，給apk打標簽，然後在initrc中將/sys/下面對應的文件chown成為systemowner，就可以了。
recovery.img生成過程
L630-L637 依賴關系
(From: build/core/Makefile)630 $(INSTALLED_RECOVERYIMAGE_TARGET): $(MKBOOTFS) $(MKBOOTIMG) $(MINIGZIP) /631 $(INSTALLED_RAMDISK_TARGET) /632 $(INSTALLED_BOOTIMAGE_TARGET) /633 $(recovery_binary) /634 $(recovery_initrc) $(recovery_kernel) /635 $(INSTALLED_2NDBOOTLOADER_TARGET) /636 $(recovery_build_prop) $(recovery_resource_deps) /637 $(RECOVERY_INSTALL_OTA_KEYS)
INSTALLED_RECOVERYIMAGE_TARGET 為我們的編譯目標：
584 INSTALLED_RECOVERYIMAGE_TARGET := $(PRODUCT_OUT)/recovery.img
它依賴很多其它目標：
1．MKBOOTFS, MINIGZIP, MKBOOTIMG，PC端工具軟體：（From build/core/config.mk）265 MKBOOTFS := $(HOST_OUT_EXECUTABLES)/mkbootfs$(HOST_EXECUTABLE_SUFFIX)266 MINIGZIP := $(HOST_OUT_EXECUTABLES)/minigzip$(HOST_EXECUTABLE_SUFFIX)267 MKBOOTIMG := $(HOST_OUT_EXECUTABLES)/mkbootimg$(HOST_EXECUTABLE_SUFFIX)
2．INSTALLED_RAMDISK_TARGET，標准根文件系統 ramdisk.img：
326 BUILT_RAMDISK_TARGET := $(PRODUCT_OUT)/ramdisk.img328 # We just build this directly to the install location.329 INSTALLED_RAMDISK_TARGET := $(BUILT_RAMDISK_TARGET) 3．INSTALLED_BOOTIMAGE_TARGET， 即boot.img,標准內核及標准根文件系統：362 INSTALLED_BOOTIMAGE_TARGET := $(PRODUCT_OUT)/boot.img
4. recovery_binary, Recovery可執行程序，源碼位於：bootable/recovery
590 recovery_binary := $(call intermediates-dir-for,EXECUTABLES,recovery)/recovery
5. recovery_initrc，recovery模式的init.rc, 位於 bootable/recovery/etc/init.rc
586 recovery_initrc := $(call include-path-for, recovery)/etc/init.rc
6. recovery_kernel, recovery 模式的kernel, 同標准內核
587 recovery_kernel := $(INSTALLED_KERNEL_TARGET) # same as a non-recovery system
7.INSTALLED_2NDBOOTLOADER_TARGET，我們不用。
8. recovery_build_prop， recovery 模式的build.prop, 同標准模式。589 recovery_build_prop := $(INSTALLED_BUILD_PROP_TARGET)
9. recovery_resource_deps， recovery 模式使用的res, 位於：recovery/custom/{proct_name}/res, 以及設備自定義部分（我們沒用到）
591 recovery_resources_common := $(call include-path-for, recovery)/custom/$(TARGET_PRODUCT)/res592 recovery_resources_private := $(strip $(wildcard $(TARGET_DEVICE_DIR)/recovery/res))593 recovery_resource_deps := $(shell find $(recovery_resources_common) 594 $(recovery_resources_private) -type f) 10. RECOVERY_INSTALL_OTA_KEYS, ota 密鑰：
618 # Generate a file containing the keys that will be read by the619 # recovery binary.620 RECOVERY_INSTALL_OTA_KEYS := /621 $(call intermediates-dir-for,PACKAGING,ota_keys)/keysL638-L655 准備內容
638 @echo ----- Making recovery image ------639 rm -rf $(TARGET_RECOVERY_OUT)640 mkdir -p $(TARGET_RECOVERY_OUT)641 mkdir -p $(TARGET_RECOVERY_ROOT_OUT)642 mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/etc643 mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/tmp
准備recovery目錄：out/target/proct/{proct_name}/recovery 及其子目錄：
./root
./root/etc
./root/tmp644 echo Copying baseline ramdisk...645 cp -R $(TARGET_ROOT_OUT) $(TARGET_RECOVERY_OUT)646 echo Modifying ramdisk contents...647 rm -rf $(TARGET_RECOVERY_ROOT_OUT)/res
從標准根文件系統拷貝所有文件， 刪除其res 目錄。
648 cp -f $(recovery_initrc) $(TARGET_RECOVERY_ROOT_OUT)/649 cp -f $(recovery_binary) $(TARGET_RECOVERY_ROOT_OUT)/sbin/ 拷貝recovery 模式的核心文件 init.rc 及 recovery 650 cp -rf $(recovery_resources_common) $(TARGET_RECOVERY_ROOT_OUT)/651 $(foreach item,$(recovery_resources_private), /652 cp -rf $(item) $(TARGET_RECOVERY_ROOT_OUT)/)653 cp $(RECOVERY_INSTALL_OTA_KEYS) $(TARGET_RECOVERY_ROOT_OUT)/res/keys 拷貝資源文件及密鑰文件。 654 cat $(INSTALLED_DEFAULT_PROP_TARGET) $(recovery_build_prop) /655 > $(TARGET_RECOVERY_ROOT_OUT)/default.prop 生成屬性文件 default.prop, 它包含了標准根文件系統的default.prop （out/target/proct/{proct_name}/root/default.prop）以及system分區的build.prop (out/target/proct/{proct_name}/system/build.prop) L656-L661 最終生成recovery.img
656 $(MKBOOTFS) $(TARGET_RECOVERY_ROOT_OUT) | $(MINIGZIP) > $(recovery_ramdisk) 壓縮recovery根文件系統 657 build/quacomm/mkimage $(PRODUCT_OUT)/ramdisk-recovery.img RECOVERY > $(PRODUCT_OUT)/ramdisk_recovery.img 加一個標識頭（RECOVERY） 658 mv $(PRODUCT_OUT)/ramdisk_recovery.img $(PRODUCT_OUT)/ramdisk-recovery.img659 $(MKBOOTIMG) $(INTERNAL_RECOVERYIMAGE_ARGS) --output $@660 @echo ----- Made recovery image -------- $@661 $(hide) $(call assert-max-image-size,$@,$(BOARD_RECOVERYIMAGE_PARTITION_SIZE),raw)
和內核一起，生成recovery.img附：Recovery 根文件系統目錄結構
$ tree
.
├── advanced_meta_init.rc
├── data
├── default.prop
├── dev
├── etc
├── init
├── init.factory.rc
├── init.goldfish.rc
├── init.quacomm.rc
├── init.rc
├── meta_init.rc
├── proc
├── res
│ ├── images
│ │ ├── icon_error.png
│ │ ├── icon_installing.png
│ │ ├── indeterminate1.png
│ │ ├── indeterminate2.png
│ │ ├── indeterminate3.png
│ │ ├── indeterminate4.png
│ │ ├── indeterminate5.png
│ │ ├── indeterminate6.png
│ │ ├── progress_empty.png
│ │ └── progress_fill.png
│ └── keys
├── sbin
│ ├── adbd
│ ├── advanced_meta_init
│ ├── meta_init
│ ├── meta_tst
│ └── recovery
├── sys
├── system
└── tmp
⑷ Android：怎麼獲取當前文件（類）所在的目錄的完整路徑
android的硬存儲是按照linux系統規則來劃分的，用於存儲客戶信息和客戶安裝的應用的是/data分區，你如果使用的是c程序的話，應該是在/data/app之類的下面，我手頭沒有板子沒法給你查。文件夾是google約定俗成的，不同廠家應該都是一樣的路徑。如果是廠家定製的應用則是在/system分區下，路徑應該是/system/app下。
如果你是一個android系統學習者，而不是應用開發者的話，我建議看看以下system/etc/initrc對於你會有很大的幫助。
⑸ android2.3系統laaboo手機recovery模式怎麼選擇
Recovery Binary 是 Android 進入 Recovery 模式所運行的程序，實現了 Recovery 模式下的功能。它由目錄
bootable/recovery 下的源代碼編譯生成。頭文件 bootable/recovery/recovery_ui.h 定義了 Recovery UI
的介面，bootable/recovery/default_recovery_ui.c 是其默認實現，每個設備可以有自己不同的實現，然後通過變數
TARGET_RECOVERY_UI_LIB 來指定，否則使用默認實現。
# bootable/recovery/Android.mk
ifeq ($(TARGET_RECOVERY_UI_LIB),)
LOCAL_SRC_FILES + = default_recovery_ui.c
else
LOCAL_STATIC_LIBRARIES + = $(TARGET_RECOVERY_UI_LIB)
endif
Recovery Image：
Recovery Image 的生成規則在文件 build/core/Makefile 中定義，具體分析如下：
# build/core/Makefile
# -----------------------------------------------------------------
# Recovery image
# If neither TARGET_NO_KERNEL nor TARGET_NO_RECOVERY are true
ifeq (,$(filter true, $(TARGET_NO_KERNEL) $(TARGET_NO_RECOVERY)
$(BUILD_TINY_ANDROID)))
INSTALLED_RECOVERYIMAGE_TARGET := $(PRODUCT_OUT)/recovery.img
recovery_initrc := $(call include-path-for, recovery)/etc/init.rc
recovery_kernel := $(INSTALLED_KERNEL_TARGET) # same as a non-recovery
system
recovery_ramdisk := $(PRODUCT_OUT)/ramdisk-recovery.img
recovery_build_prop := $(INSTALLED_BUILD_PROP_TARGET)
recovery_binary := $(call
intermediates-dir-for,EXECUTABLES,recovery)/recovery
recovery_resources_common := $(call include-path-for, recovery)/res
recovery_resources_private := $(strip
$(wildcard$(TARGET_DEVICE_DIR)/recovery/res))
recovery_resource_deps := $(shell find $(recovery_resources_common) \
$(recovery_resources_private) -type f)
recovery_fstab := $(strip $(wildcard
$(TARGET_DEVICE_DIR)/recovery.fstab))
recovery_mmc_fstab := $(strip
$(wildcard$(TARGET_DEVICE_DIR)/recovery_mmc.fstab))
ifeq ($(recovery_resources_private),)
$(info No private recovery resources for TARGET_DEVICE
$(TARGET_DEVICE))
endif
ifeq ($(recovery_fstab),)
$(info No recovery.fstab for TARGET_DEVICE $(TARGET_DEVICE))
endif
INTERNAL_RECOVERYIMAGE_ARGS := \
$(addprefix --second ,$(INSTALLED_2NDBOOTLOADER_TARGET)) \
--kernel $(recovery_kernel) \
--ramdisk $(recovery_ramdisk)
# Assumes this has already been stripped
ifdef BOARD_KERNEL_CMDLINE
INTERNAL_RECOVERYIMAGE_ARGS += --cmdline "$(BOARD_KERNEL_CMDLINE)"
endif
ifdef BOARD_KERNEL_BASE
INTERNAL_RECOVERYIMAGE_ARGS += --base $(BOARD_KERNEL_BASE)
endif
BOARD_KERNEL_PAGESIZE := $(strip $(BOARD_KERNEL_PAGESIZE))
ifdef BOARD_KERNEL_PAGESIZE
INTERNAL_RECOVERYIMAGE_ARGS += --pagesize $(BOARD_KERNEL_PAGESIZE)
endif
INSTALLED_BOOTIMAGE_TARGET := $(PRODUCT_OUT)/boot.img
kernel: $(INSTALLED_BOOTIMAGE_TARGET)
.PHONY: kernel
# Keys authorized to sign OTA packages this build will accept. The
# build always uses test-keys for this; release packaging tools will
# substitute other keys for this one.
OTA_PUBLIC_KEYS := $(SRC_TARGET_DIR)/proct/security/testkey.x509.pem
# Generate a file containing the keys that will be read by the
# recovery binary.
RECOVERY_INSTALL_OTA_KEYS := \
$(call intermediates-dir-for,PACKAGING,ota_keys)/keys
DUMPKEY_JAR := $(HOST_OUT_java_LIBRARIES)/mpkey.jar
$(RECOVERY_INSTALL_OTA_KEYS): PRIVATE_OTA_PUBLIC_KEYS :=
$(OTA_PUBLIC_KEYS)
$(RECOVERY_INSTALL_OTA_KEYS): $(OTA_PUBLIC_KEYS) $(DUMPKEY_JAR)
@echo "DumpPublicKey: $@ <= $(PRIVATE_OTA_PUBLIC_KEYS)"
@rm -rf $@
@mkdir -p $(dir $@)
java -jar $(DUMPKEY_JAR) $(PRIVATE_OTA_PUBLIC_KEYS) > $@
$(INSTALLED_RECOVERYIMAGE_TARGET): $(MKBOOTFS) $(MKBOOTIMG) $(MINIGZIP)
\
$(INSTALLED_RAMDISK_TARGET) \
$(INSTALLED_BOOTIMAGE_TARGET) \
$(recovery_binary) \
$(recovery_initrc) $(recovery_kernel) \
$(INSTALLED_2NDBOOTLOADER_TARGET) \
$(recovery_build_prop) $(recovery_resource_deps) \
$(recovery_fstab) \
$(RECOVERY_INSTALL_OTA_KEYS)
/* 以正常系統的根文件系統為基礎構建 Recovery 的根文件系統 */
@echo ----- Making recovery image ------
rm -rf $(TARGET_RECOVERY_OUT)
mkdir -p $(TARGET_RECOVERY_OUT)
mkdir -p $(TARGET_RECOVERY_ROOT_OUT)
mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/etc
mkdir -p $(TARGET_RECOVERY_ROOT_OUT)/tmp
echo Copying baseline ramdisk...
cp -R $(TARGET_ROOT_OUT) $(TARGET_RECOVERY_OUT)
/* 刪除所有的 Init 腳本，使用 Recovery 特定的 Init 腳本 */
rm $(TARGET_RECOVERY_ROOT_OUT)/init*.rc
echo Modifying ramdisk contents...
cp -f $(recovery_initrc) $(TARGET_RECOVERY_ROOT_OUT)/
/* 添加 Recovery Binary */
cp -f $(recovery_binary) $(TARGET_RECOVERY_ROOT_OUT)/sbin/
/* 添加通用的和設備特定的 Recovery 資源 */
cp -rf $(recovery_resources_common) $(TARGET_RECOVERY_ROOT_OUT)/
$(foreach item,$(recovery_resources_private), \
cp -rf $(item) $(TARGET_RECOVERY_ROOT_OUT)/)
/* 添加設備特定的文件系統表 */
$(foreach item,$(recovery_fstab), \
cp -f $(item) $(TARGET_RECOVERY_ROOT_OUT)/etc/recovery.fstab)
$(foreach item,$(recovery_mmc_fstab), \
cp -f $(item) $(TARGET_RECOVERY_ROOT_OUT)/etc/recovery_mmc.fstab)
/* 內嵌驗證簽名的公鑰 */
cp $(RECOVERY_INSTALL_OTA_KEYS) $(TARGET_RECOVERY_ROOT_OUT)/res/keys
/* 生成 Recovery 模式的默認屬性文件 */
cat $(INSTALLED_DEFAULT_PROP_TARGET) $(recovery_build_prop) \
> $(TARGET_RECOVERY_ROOT_OUT)/default.prop
/* 生成 Recovery 的根文件系統 ramdisk-recovery.img */
$(MKBOOTFS) $(TARGET_RECOVERY_ROOT_OUT) | $(MINIGZIP) >
$(recovery_ramdisk)
/* 把正常系統的內核跟 ramdisk-recovery.img 打包生成 Recovery Image */
$(MKBOOTIMG) $(INTERNAL_RECOVERYIMAGE_ARGS) --output $@
@echo ----- Made recovery image -------- $@
/* 驗證生成的 Recovery Image 有沒有超出 Recovery 分區的大小 */
$(hide) $(call
assert-max-image-size,$@,$(BOARD_RECOVERYIMAGE_PARTITION_SIZE),raw)
else
INSTALLED_RECOVERYIMAGE_TARGET :=
endif
.PHONY: recoveryimage
recoveryimage: $(INSTALLED_RECOVERYIMAGE_TARGET)
Recovery Init Script：
從上面的分析可以看出 recovery.img 和 boot.img 的區別不大，主要是 init 腳本不一樣，recovery 的 init
腳本相對簡單，系統起來後只運行 ueventd、recovery、adbd 三個服務。
# bootable/recovery/etc/init.rc
on early-init
start ueventd
on init
export PATH /sbin
export ANDROID_ROOT /system
export ANDROID_DATA /data
export EXTERNAL_STORAGE /sdcard
symlink /system/etc /etc
mkdir /sdcard
mkdir /system
mkdir /data
mkdir /cache
mount /tmp /tmp tmpfs
on boot
ifup lo
hostname localhost
domainname localdomain
class_start default
service ueventd /sbin/ueventd
critical
service recovery /sbin/recovery
service adbd /sbin/adbd recovery
disabled
on property:persist.service.adb.enable=1
start adbd
on property:persist.service.adb.enable=0
stop adbd
Android <----> Recovery Binary <----> Bootloader：
有時候 Android 需要不同的模式互相協助來完成一項任務，這樣不同模式之間就要有一種機制來交換信息。Recovery Binary 和
Bootloader 之間是通過 misc 分區來傳遞信息的，如果是 MTD 設備，則使用 misc 分區的第二個頁面，如果是塊設備，則使用 misc
分區的第一塊，交換的信息通過如下結構體封裝。Recovery Binary 和 Android 之間是通過 cache
分區下的如下幾個固定文件來傳遞信息的。
/* Recovery Binary <----> Bootloader */
struct bootloader_message {
char command[ 32];
char status[ 32];
char recovery[ 1024];
};
/* Recovery Binary <----> Android */
/cache/recovery/command
/cache/recovery/intent
/cache/recovery/log
/cache/recovery/last_log
Updater Binary：
Updater Binary 是 OTA package 的安裝程序，被打包到 OTA package 中一起發布。Updater Binary
的源代碼位於目錄 bootable/recovery/updater 中。每個設備都可以為 Updater Binary
添加自己特定的擴展，然後通過變數TARGET_RECOVERY_UPDATER_LIBS 和
TARGET_RECOVERY_UPDATER_EXTRA_LIBS 來指定。
# bootable/recovery/updater/Android.mk
LOCAL_STATIC_LIBRARIES += $(TARGET_RECOVERY_UPDATER_LIBS) \
$(TARGET_RECOVERY_UPDATER_EXTRA_LIBS)
LOCAL_STATIC_LIBRARIES + = libapplypatch libedify libmttils libminzip
libz
LOCAL_STATIC_LIBRARIES + = libmincrypt libbz
LOCAL_STATIC_LIBRARIES + = libcutils libstdc++ libc
LOCAL_C_INCLUDES + = $(LOCAL_PATH)/..
# Each library in TARGET_RECOVERY_UPDATER_LIBS should have a function
# named "Register_()". Here we emit a little C function that
# gets #included by updater.c. It calls all those registration
# functions.
# Devices can also add libraries to TARGET_RECOVERY_UPDATER_EXTRA_LIBS.
# These libs are also linked in with updater, but we don't try to call
# any sort of registration function for these. Use this variable for
# any subsidiary static libraries required for your registered
# extension libs.
inc := $(call
intermediates-dir-for,PACKAGING,updater_extensions)/register.inc
# During the first pass of reading the makefiles, we mp the list of
# extension libs to a temp file, then that to the ".list" file if
# it is different than the existing .list (if any). The register.inc
# file then uses the .list as a prerequisite, so it is only rebuilt
# (and updater.o recompiled) when the list of extension libs changes.
junk := $(shell mkdir -p $(dir $(inc));\
echo $(TARGET_RECOVERY_UPDATER_LIBS) > $(inc).temp;\
diff -q $(inc).temp $(inc).list || cp -f $(inc).temp $(inc).list)
$(inc) : libs := $(TARGET_RECOVERY_UPDATER_LIBS)
$(inc) : $(inc).list
$(hide) mkdir -p $(dir $@)
$(hide) echo "" > $@
$(hide) $(foreach lib,$(libs),echo "extern void Register_$(lib)(void);"
>> $@)
$(hide) echo "void RegisterDeviceExtensions() {" >> $@
$(hide) $(foreach lib,$(libs),echo " Register_$(lib)();" >> $@)
$(hide) echo "}" >> $@
$(call intermediates-dir-for,EXECUTABLES,updater)/updater.o : $(inc)
LOCAL_C_INCLUDES += $(dir $(inc))