自 2025 年 3 月 27 日起，我們建議您使用 android-latest-release 而非 aosp-main 建構及貢獻 AOSP。詳情請參閱「Android 開放原始碼計畫變更」。
裝置設定
透過集合功能整理內容
你可以依據偏好儲存及分類內容。
外部儲存空間由 vold 初始服務和 StorageManagerService 系統服務共同管理。物理外部儲存空間磁碟區的掛接作業由 vold 處理，該程序會執行測試操作，在將媒體提供給應用程式前先行準備。
注意：在 Android 8.0 中，MountService 類別已重新命名為 StorageManagerService。
檔案對應
針對 Android 4.2.2 以下版本，裝置專屬的 vold.fstab 設定檔會定義從 sysfs 裝置到檔案系統掛載點的對應項目，每行內容皆遵循以下格式：
dev_mount <label> <mount_point> <partition> <sysfs_path> [flags]
label：音量標籤。mount_point：磁碟區應掛接的檔案系統路徑。partition：分區編號 (以 1 為基底)，或「auto」表示第一個可用分區。sysfs_path：一或多個 sysfs 路徑，可連結至可提供此掛載點的裝置。以空格分隔，且每個項目都必須以 / 開頭。flags：標記的選用逗號分隔清單，不得包含 /。可能的值包括 nonremovable 和 encryptable。
針對 Android 4.3 以上版本，init、vold 和 recovery 使用的各種 fstab 檔案已在 /fstab.<device> 檔案中統一。對於由 vold 管理的外部儲存空間磁碟區，項目應採用以下格式：
<src> <mnt_point> <type> <mnt_flags> <fs_mgr_flags>
src：sysfs 底下的路徑 (通常會掛接至 /sys)，可提供裝置的掛接點。路徑開頭必須為 /。mount_point：磁碟區應掛接的檔案系統路徑。type：音量中的檔案系統類型。對於外部資訊卡，這個值通常為 vfat。mnt_flags：Vold 會忽略這個欄位，因此應將其設為 defaultsfs_mgr_flags：Vold 會忽略統一 fstab 中不含此欄位 voldmanaged= 旗標的任何一行。這個旗標後面必須接著描述卡片的標籤，以及分區編號或 auto 字詞。範例如下：voldmanaged=sdcard:auto。其他可能的旗標為 nonremovable、encryptable=sdcard、noemulatedsd 和 encryptable=userdata。
設定詳細資料
在架構層級以上，外部儲存空間互動會透過 StorageManagerService 處理。由於 Android 6.0 的設定有所變更 (例如移除 storage_list.xml 資源疊加層)，因此設定詳細資料分為兩個類別。
Android 5.x 以下版本
裝置專屬的 storage_list.xml 設定檔通常會透過 frameworks/base 重疊提供，用於定義儲存裝置的屬性和限制。<StorageList> 元素包含一或多個 <storage> 元素，其中應標示為主要元素的只有一個。<storage> 屬性包括：
mountPoint：此掛載點的檔案系統路徑。storageDescription：描述此掛載點的字串資源。primary：如果此掛載點是主要外部儲存空間，則為 true。removable：如果此掛載點含有可移除的媒體 (例如實體 SD 卡)，則為 true。emulated：如果此掛載點為模擬的，且由內部儲存空間提供支援 (可能會使用 FUSE 守護程式)，則為 true。mtp-reserve：MTP 應為可用儲存空間保留的 MB 數量。只有在掛載點標示為模擬時才會使用。allowMassStorage：如果此掛載點可透過 USB 大量儲存空間共用，則為 true。maxFileSize：檔案大小上限 (MB)。
裝置可以透過模擬內部儲存空間所支援的大小寫不敏感、無權限的檔案系統，提供外部儲存空間。system/core/sdcard 中的 FUSE 守護程序提供一種可能的實作方式，可新增為特定裝置的 init.rc 服務：
# virtual sdcard daemon running as media_rw (1023)
service sdcard /system/bin/sdcard <source_path> <dest_path> 1023 1023
class late_start
其中 source_path 是備援內部儲存空間，而 dest_path 是目標掛接點。
設定裝置專屬的 init.rc 指令碼時，必須將 EXTERNAL_STORAGE 環境變數定義為主要外部儲存空間的路徑。/sdcard 路徑也必須解析至相同位置，可能會透過符號連結。如果裝置在平台更新期間調整外部儲存空間的位置，應建立符號連結，以便舊路徑繼續運作。
Android 6.0
儲存空間子系統的設定現在集中在特定裝置的 fstab 檔案中，且已移除多個歷來提供的靜態設定檔/變數，以便支援更多動態行為：
storage_list.xml 資源重疊已移除，且架構不再使用。vold 偵測到儲存裝置時，現在會動態設定儲存裝置。EMULATED_STORAGE_SOURCE/TARGET 環境變數已遭移除，Zygote 不再使用這些變數來設定使用者專屬的掛載點。相反地，現在會使用使用者專屬的 GID 強制執行使用者分離，並在執行階段由 vold 掛載主要共用儲存空間。
- 開發人員可以根據用途，繼續以動態或靜態方式建構路徑。在路徑中加入 UUID 可識別每張資訊卡，讓開發人員更清楚瞭解位置。(例如，
/storage/ABCD-1234/report.txt 與 /storage/DCBA-4321/report.txt 顯然屬於不同的檔案)。
- 硬式編碼的 FUSE 服務已從裝置專屬的
init.rc 檔案中移除，並在需要時從 vold 動態分支。
除了這些設定變更之外，Android 6.0 還包含可採用儲存空間的概念。對於 Android 6.0 裝置，未採用的任何實體媒體都會視為可攜式。
合併儲存空間
如要在 fstab 中指出可採用的儲存空間裝置，請在 fs_mgr_flags 欄位中使用 encryptable=userdata 屬性。以下是常見的定義：
/devices/platform/mtk-msdc.1/mmc_host* auto auto defaults
voldmanaged=sdcard1:auto,encryptable=userdata
採用儲存裝置時，平台會清除內容，並寫入 GUID 分區表，定義兩個分區：
- 保留供日後使用的空白小
android_meta 區隔。分區類型 GUID 為 19A710A2-B3CA-11E4-B026-10604B889DCF。 - 大型
android_ext 分區，使用 dm-crypt 加密，並視核心功能使用 ext4 或 f2fs 格式化。分割區類型 GUID 為 193D1EA4-B3CA-11E4-B075-10604B889DCF。
可攜式儲存空間
在 fstab 中，如果沒有定義 encryptable=userdata 等其他屬性，系統會將具有 voldmanaged 屬性的儲存裝置視為可攜式裝置。舉例來說，以下是 USB OTG 裝置的一般定義：
/devices/*/xhci-hcd.0.auto/usb* auto auto defaults
voldmanaged=usb:auto
平台會在掛載前使用 blkid 偵測檔案系統類型，使用者可以在檔案系統不相容時選擇格式化媒體。
這個頁面中的內容和程式碼範例均受《內容授權》中的授權所規範。Java 與 OpenJDK 是 Oracle 和/或其關係企業的商標或註冊商標。
上次更新時間：2025-07-27 (世界標準時間)。
[[["容易理解","easyToUnderstand","thumb-up"],["確實解決了我的問題","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["缺少我需要的資訊","missingTheInformationINeed","thumb-down"],["過於複雜/步驟過多","tooComplicatedTooManySteps","thumb-down"],["過時","outOfDate","thumb-down"],["翻譯問題","translationIssue","thumb-down"],["示例/程式碼問題","samplesCodeIssue","thumb-down"],["其他","otherDown","thumb-down"]],["上次更新時間：2025-07-27 (世界標準時間)。"],[],[],null,["# Device configuration\n\nExternal storage is managed by a combination of the `vold` init\nservice and `StorageManagerService` system service. Mounting of\nphysical external storage volumes is handled by `vold`, which\nperforms staging operations to prepare the media before exposing it to apps.\n\n**Note:** In Android 8.0, the\n`MountService` class was renamed to\n`StorageManagerService`.\n\nFile mappings\n-------------\n\nFor Android 4.2.2 and earlier, the device-specific `vold.fstab`\nconfiguration file defines mappings from sysfs devices to filesystem mount\npoints, and each line follows this format: \n\n```\ndev_mount \u003clabel\u003e \u003cmount_point\u003e \u003cpartition\u003e \u003csysfs_path\u003e [flags]\n```\n\n- `label`: Label for the volume.\n- `mount_point`: Filesystem path where the volume should be mounted.\n- `partition`: Partition number (1 based), or 'auto' for first usable partition.\n- `sysfs_path`: One or more sysfs paths to devices that can provide this mount point. Separated by spaces, and each must start with `/`.\n- `flags`: Optional comma separated list of flags, must not contain `/`. Possible values include `nonremovable` and `encryptable`.\n\nFor Android releases 4.3 and later, the various fstab files used by init, vold and\nrecovery were unified in the `/fstab.\u003cdevice\u003e` file. For external\nstorage volumes that are managed by `vold`, the entries should have the\nfollowing format: \n\n```\n\u003csrc\u003e \u003cmnt_point\u003e \u003ctype\u003e \u003cmnt_flags\u003e \u003cfs_mgr_flags\u003e\n```\n\n- `src`: A path under sysfs (usually mounted at /sys) to the device that can provide the mount point. The path must start with `/`.\n- `mount_point`: Filesystem path where the volume should be mounted.\n- `type`: The type of the filesystem on the volume. For external cards, this is usually `vfat`.\n- `mnt_flags`: `Vold` ignores this field and it should be set to `defaults`\n- `fs_mgr_flags`: `Vold` ignores any lines in the unified fstab that do not include the `voldmanaged=` flag in this field. This flag must be followed by a label describing the card, and a partition number or the word `auto`. Here is an example: `voldmanaged=sdcard:auto`. Other possible flags are `nonremovable`, `encryptable=sdcard`, `noemulatedsd`, and `encryptable=userdata`.\n\nConfiguration details\n---------------------\n\nExternal storage interactions at and above the framework level are handled\nthrough `StorageManagerService`. Due to configuration changes in\nAndroid 6.0 (like the removal of the storage_list.xml resource overlay), the\nconfiguration details are split into two categories.\n\n### Android 5.x and earlier\n\nThe device-specific `storage_list.xml` configuration\nfile, typically provided through a `frameworks/base` overlay, defines the\nattributes and constraints of storage devices. The `\u003cStorageList\u003e` element\ncontains one or more `\u003cstorage\u003e` elements, exactly one of which should be marked\nprimary. `\u003cstorage\u003e` attributes include:\n\n- `mountPoint`: filesystem path of this mount.\n- `storageDescription`: string resource that describes this mount.\n- `primary`: true if this mount is the primary external storage.\n- `removable`: true if this mount has removable media, such as a physical SD card.\n- `emulated`: true if this mount is emulated and is backed by internal storage, possibly using a FUSE daemon.\n- `mtp-reserve`: number of MB of storage that MTP should reserve for free storage. Only used when mount is marked as emulated.\n- `allowMassStorage`: true if this mount can be shared via USB mass storage.\n- `maxFileSize`: maximum file size in MB.\n\nDevices may provide external storage by emulating a case-insensitive,\npermissionless filesystem backed by internal storage. One possible\nimplementation is provided by the FUSE daemon in `system/core/sdcard`, which can\nbe added as a device-specific `init.rc` service: \n\n```\n# virtual sdcard daemon running as media_rw (1023)\nservice sdcard /system/bin/sdcard \u003csource_path\u003e \u003cdest_path\u003e 1023 1023\n class late_start\n```\n\nWhere `source_path` is the backing internal storage and `dest_path` is the\ntarget mount point.\n\nWhen configuring a device-specific `init.rc` script, the `EXTERNAL_STORAGE`\nenvironment variable must be defined as the path to the primary external\nstorage. The `/sdcard` path must also resolve to the same location, possibly\nthrough a symlink. If a device adjusts the location of external storage between\nplatform updates, symlinks should be created so that old paths continue working.\n\n### Android 6.0\n\nConfiguration of the storage subsystem is now concentrated in the\ndevice-specific `fstab` file, and several historical static configuration files/variables have been\nremoved to support more dynamic behavior:\n\n- The `storage_list.xml` resource overlay has been removed and is no longer used by the framework. Storage devices are now configured dynamically when detected by `vold`.\n- The `EMULATED_STORAGE_SOURCE/TARGET` environment variables have been removed and are no longer used by Zygote to configure user-specific mount points. Instead, user separation is now enforced with user-specific GIDs, and primary shared storage is mounted into place by `vold` at runtime.\n - Developers may continue to build paths dynamically or statically depending on their use case. Including the UUID in the path identifies each card to make location clearer for developers. (For example, `/storage/ABCD-1234/report.txt` is clearly a different file than `/storage/DCBA-4321/report.txt`.)\n- The hard-coded FUSE services have been removed from device-specific `init.rc` files and are instead forked dynamically from `vold` when needed.\n\nIn addition to these configuration changes, Android 6.0 includes the notion of\nadoptable storage. For Android 6.0 devices, any physical media that is not\nadopted is viewed as portable.\n\n#### Adoptable storage\n\nTo indicate an adoptable storage device in the `fstab`, use the `encryptable=userdata` attribute in the `fs_mgr_flags` field. Here's a typical definition: \n\n```\n/devices/platform/mtk-msdc.1/mmc_host* auto auto defaults\nvoldmanaged=sdcard1:auto,encryptable=userdata\n```\n\nWhen a storage device is adopted, the platform erases the contents and writes a\nGUID partition table that defines two partitions:\n\n- a small empty `android_meta` partition that is reserved for future use. The partition type GUID is 19A710A2-B3CA-11E4-B026-10604B889DCF.\n- a large `android_ext` partition that is encrypted using dm-crypt and formatted using either `ext4` or `f2fs` depending on the kernel capabilities. The partition type GUID is 193D1EA4-B3CA-11E4-B075-10604B889DCF.\n\n#### Portable storage\n\nIn the `fstab`, storage devices with the `voldmanaged` attribute are considered to be portable by default unless another attribute\nlike `encryptable=userdata` is defined. For example, here's a typical definition for USB OTG devices: \n\n```\n/devices/*/xhci-hcd.0.auto/usb* auto auto defaults\n voldmanaged=usb:auto\n```\n\nThe platform uses `blkid` to detect filesystem types before mounting, and users can choose to format the\nmedia when the filesystem is unsupported."]]
