Android 系统分区分析
Android系统分区
Android系统开发时，经常会遇到添加或者调整系统分区大小的问题，下面以mstar的一款产品为例进行分析：
（1）mount指令可以查看到板子中挂在的分区，主要关注ext4类型分区，例如tvservice，tvconfig，tvconfig，tvcustomer
130|shell@arbutus:/ # mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,nosuid,relatime,mode=755 0 0
devpts /dev/pts devpts rw,relatime,mode=600 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
none /sys/fs/cgroup tmpfs rw,relatime,mode=750,gid=1000 0 0
tmpfs /mnt/asec tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=1000 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
tmpfs /mnt/usb tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /mnt/iso tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /mnt/samba tmpfs rw,relatime,mode=755,gid=1000 0 0
tmpfs /var tmpfs rw,relatime,mode=775,gid=1000 0 0
/dev/block/platform/mstar_mci.0/by-name/system /system ext4 ro,relatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/cache /cache ext4 rw,nosuid,nodev,noatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/userdata /data ext4 rw,nosuid,nodev,noatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/tvservice /tvservice ext4 ro,relatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/tvconfig /tvconfig ext4 ro,relatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/tvdatabase /tvdatabase ext4 rw,nosuid,nodev,noatime,data=ordered 0 0
/dev/block/platform/mstar_mci.0/by-name/tvcustomer /tvcustomer ext4 rw,nosuid,nodev,noatime,data=ordered 0 0
/dev/fuse /mnt/sdcard fuse rw,nosuid,nodev,noexec,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0（2）查看分区文件fstab.monet (device/mstar/arbutus/目录下)，截取部分信息如下：
/dev/block/platform/mstar_mci.0/by-name/system /system ext4 ro wait
/dev/block/platform/mstar_mci.0/by-name/cache /cache ext4 noatime,nosuid,nodev wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci.0/by-name/userdata /data ext4 noatime,nosuid,nodev wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci.0/by-name/tvservice /tvservice ext4 ro wait
/dev/block/platform/mstar_mci.0/by-name/tvconfig /tvconfig ext4 ro wait
/dev/block/platform/mstar_mci.0/by-name/tvdatabase /tvdatabase ext4 noatime,nosuid,nodev wait,block_validity,nodiscard,data=ordered,journal_checksum
/dev/block/platform/mstar_mci.0/by-name/tvcustomer /tvcustomer ext4 noatime,nosuid,nodev android平台不同厂商可能名称不一样，但是都是fstab.xxx的形式
（3）指定各个分区的大小，BoardConfig.mk (device/mstar/arbutus)文件指定各自大小可以根据需要进行修改
# mmc part
# : type name (size)
#1. misc (512K)
#2. recovery (19M)
#3. boot (15M)
#4. tee (6M)
#5. rtpm (256K)
#6. dtb (1M)
#7. system (800M)
#8. userdata (900M)
#9. cache (1G)
#10. tvservice (160M)
#11. tvconfig (10M)
#12. tvdatabase (8M)
#13. tvcustomer (16M)
BOARD_RECOVERYIMAGE_PARTITION_SIZE := 0x01300000
BOARD_BOOTIMAGE_PARTITION_SIZE := 0x00F00000
BOARD_TEEIMAGE_PARTITION_SIZE := 0x00600000
BOARD_RTPMIMAGE_PARTITION_SIZE := 0x00040000
BOARD_DTBIMAGE_PARTITION_SIZE := 0x00100000
BOARD_SYSTEMIMAGE_PARTITION_SIZE := 0x33C00000
BOARD_USERDATAIMAGE_PARTITION_SIZE := 0x38000000
BOARD_CACHEIMAGE_PARTITION_SIZE := 0x40000000
BOARD_TVSERVICEIMAGE_PARTITION_SIZE := 0x0A000000
BOARD_TVCONFIGIMAGE_PARTITION_SIZE := 0x00A00000
BOARD_TVDATABASEIMAGE_PARTITION_SIZE := 0x00800000
BOARD_TVCUSTOMERIMAGE_PARTITION_SIZE := 0x01000000
BOARD_FLASH_BLOCK_SIZE := 512（4）启动脚本加载，init.monet.rc脚本中on fs 模块中启动
on fs
mkdir /tvservice
mkdir /tvconfig
mkdir /tvdatabase
mkdir /tvcustomer
mount_all /fstab.monet（5）init进程解析fstab.monet文件
keywords.h文件中注册mount_all操作方法
enum {
K_UNKNOWN,
#endif
KEYWORD(capability, OPTION, 0, 0)
KEYWORD(chdir, COMMAND, 1, do_chdir)
KEYWORD(chroot, COMMAND, 1, do_chroot)
KEYWORD(class, OPTION, 0, 0)
KEYWORD(class_start, COMMAND, 1, do_class_start)
KEYWORD(class_stop, COMMAND, 1, do_class_stop)
KEYWORD(class_reset, COMMAND, 1, do_class_reset)
KEYWORD(console, OPTION, 0, 0)
KEYWORD(critical, OPTION, 0, 0)
KEYWORD(disabled, OPTION, 0, 0)
KEYWORD(domainname, COMMAND, 1, do_domainname)
KEYWORD(enable, COMMAND, 1, do_enable)
KEYWORD(exec, COMMAND, 1, do_exec)
KEYWORD(export, COMMAND, 2, do_export)
KEYWORD(group, OPTION, 0, 0)
KEYWORD(hostname, COMMAND, 1, do_hostname)
KEYWORD(ifup, COMMAND, 1, do_ifup)
KEYWORD(insmod, COMMAND, 1, do_insmod)
KEYWORD(import, SECTION, 1, 0)
KEYWORD(keycodes, OPTION, 0, 0)
KEYWORD(mkdir, COMMAND, 1, do_mkdir)
KEYWORD(mount_all, COMMAND, 1, do_mount_all)
KEYWORD(mount, COMMAND, 3, do_mount)
KEYWORD(on, SECTION, 0, 0)
KEYWORD(oneshot, OPTION, 0, 0)
KEYWORD(onrestart, OPTION, 0, 0)
KEYWORD(powerctl, COMMAND, 1, do_powerctl)
KEYWORD(restart, COMMAND, 1, do_restart)
KEYWORD(restorecon, COMMAND, 1, do_restorecon)
KEYWORD(restorecon_recursive, COMMAND, 1, do_restorecon_recursive)
KEYWORD(rm, COMMAND, 1, do_rm)
KEYWORD(rmdir, COMMAND, 1, do_rmdir)
KEYWORD(seclabel, OPTION, 0, 0)
KEYWORD(service, SECTION, 0, 0)
KEYWORD(setcon, COMMAND, 1, do_setcon)
KEYWORD(setenforce, COMMAND, 1, do_setenforce)
KEYWORD(setenv, OPTION, 2, 0)
KEYWORD(setkey, COMMAND, 0, do_setkey)
KEYWORD(setprop, COMMAND, 2, do_setprop)
KEYWORD(setrlimit, COMMAND, 3, do_setrlimit)
KEYWORD(setsebool, COMMAND, 2, do_setsebool)
KEYWORD(socket, OPTION, 0, 0)
KEYWORD(start, COMMAND, 1, do_start)
KEYWORD(stop, COMMAND, 1, do_stop)
KEYWORD(swapon_all, COMMAND, 1, do_swapon_all)
KEYWORD(trigger, COMMAND, 1, do_trigger)
KEYWORD(symlink, COMMAND, 1, do_symlink)
KEYWORD(sysclktz, COMMAND, 1, do_sysclktz)
KEYWORD(user, OPTION, 0, 0)
KEYWORD(wait, COMMAND, 1, do_wait)
KEYWORD(write, COMMAND, 2, do_write)
KEYWORD(copy, COMMAND, 2, do_copy)
KEYWORD(chown, COMMAND, 2, do_chown)
KEYWORD(chmod, COMMAND, 2, do_chmod)
KEYWORD(loglevel, COMMAND, 1, do_loglevel)
KEYWORD(load_persist_props, COMMAND, 0, do_load_persist_props)
KEYWORD(load_all_props, COMMAND, 0, do_load_all_props)
KEYWORD(ioprio, OPTION, 0, 0)
#ifdef __MAKE_KEYWORD_ENUM__
KEYWORD_COUNT,
}builtins.c文件中do_mount_all，启动一个进程调用fs_mgr_read_fstab，fs_mgr_mount_all启动解析，其中system\core\fs_mgr有被vold，adb等模块用来解析
fstab.xxx等分区文件。
（6）根据第三步中指定的分区大小，进行打包对应分区的img文件
releaseimage.sh, mkimage.sh, build_image.sh, make_usb_upgrade.sh等脚本中，会根据第三步设置的大小来制作img文件
如mkimage.sh
function make-images()
{
mkdir -p $RELEASE_OUT
mkdir -p $RELEASE_OUT/scripts
gernerate-script-start
# Raw partition must be first.
make-raw-partition
make-split-fs-partition system $BOARD_SYSTEMIMAGE_PARTITION_SIZE true
make-fs-partition userdata $BOARD_USERDATAIMAGE_PARTITION_SIZE true
make-fs-partition cache $BOARD_CACHEIMAGE_PARTITION_SIZE true
make-fs-partition tvservice $BOARD_TVSERVICEIMAGE_PARTITION_SIZE false
make-fs-partition tvconfig $BOARD_TVCONFIGIMAGE_PARTITION_SIZE false
make-fs-partition tvdatabase $BOARD_TVDATABASEIMAGE_PARTITION_SIZE false
make-fs-partition tvcustomer $BOARD_TVCUSTOMERIMAGE_PARTITION_SIZE false
......
......
}
buiild_image.sh文件
#make-fs-partition $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO
function make-fs-partition()
{
echo -e "\033[31mMake fs $1 partition...\033[0m"
local PARTITION_NAME=$1
local PARTITION_SIZE=$2
local PARTITION_LZO=$3
# Generate image
gernerate-fs-image $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO
release-fs-partition $PARTITION_NAME $PARTITION_SIZE $PARTITION_LZO
}function gernerate-fs-image()
{
local PARTITION_NAME=$1
local PARTITION_SIZE=$2
local PARTITION_LZO=$3
if [ "$PARTITION_NAME" == "userdata" ]; then
local MOUNT_POINT=data
else
local MOUNT_POINT=$PARTITION_NAME
fi
local TARGET_OUT=$PRODUCT_OUT/$MOUNT_POINT
if [ ! -d "$TARGET_OUT" ]; then
echo "No $TARGET_OUT directory to gernerate image."
return
fi
if [ "$PARTITION_NAME" == "system" -o "$PARTITION_NAME" == "userdata" -o "$PARTITION_NAME" == "cache" -o "$PARTITION_NAME" == "systembackup" ]; then
if [ $PARTITION_NAME == "system" ]; then
local IMAGE_INFO=$PRODUCT_OUT/obj/PACKAGING/systemimage_intermediates/system_image_info.txt
else
local IMAGE_INFO=$PRODUCT_OUT/obj/PACKAGING/"$PARTITION_NAME"_intermediates/"$PARTITION_NAME"_image_info.txt
fi
generate-userimage-prop-dictionary $IMAGE_INFO
./build/tools/releasetools/build_image.py $TARGET_OUT $IMAGE_INFO $PRODUCT_OUT/$PARTITION_NAME.img
else
make_ext4fs -S $PRODUCT_OUT/root/file_contexts -l $PARTITION_SIZE -a $MOUNT_POINT $PRODUCT_OUT/$PARTITION_NAME.img $TARGET_OUT
fi
}（7）最后make_use_upgrade.sh打包，发布整体软件。