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systemcorefs_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 " 33[31mMake fs $1 partition... 33[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 <span style="background-color: rgb(0, 102, 0);">make_ext4fs -S $PRODUCT_OUT/root/file_contexts -l $PARTITION_SIZE -a $MOUNT_POINT $PRODUCT_OUT/$PARTITION_NAME.img $TARGET_OUT</span> fi }