自 2025 年 3 月 27 日起，我们建议您使用 android-latest-release 而非 aosp-main 构建 AOSP 并为其做出贡献。如需了解详情，请参阅 AOSP 的变更。
设备配置
使用集合让一切井井有条
根据您的偏好保存内容并对其进行分类。
外部存储空间由 vold init 服务和 StorageManagerService 系统服务共同管理。外部实体存储卷的装载由 vold 处理：通过执行分阶段操作准备好媒体，然后再将其提供给应用。
注意：在 Android 8.0 中，MountService 类已更名为 StorageManagerService。
文件映射
对于 Android 4.2.2 及更低版本，特定于设备的 vold.fstab 配置文件定义从 sysfs 设备到文件系统装载点的映射，每行都遵循以下格式：
dev_mount <label> <mount_point> <partition> <sysfs_path> [flags]
label：卷的标签。mount_point：要装载卷的文件系统路径。partition：分区编号（从 1 开始）；如果是第一个可用分区，则为“auto”。sysfs_path：可以提供此装载点的设备的一个或多个 sysfs 路径。这些路径用空格分开，且必须都以 / 开头。flags：（可选）以英文逗号分隔的标记列表，不能包含 /。可能的值包括 nonremovable 和 encryptable。
对于 Android 4.3 及更高版本，init、vold 和 recovery 所使用的各种 fstab 文件在 /fstab.<device> 文件中进行统一。对于由 vold 管理的外部存储卷，条目应采用以下格式：
<src> <mnt_point> <type> <mnt_flags> <fs_mgr_flags>
src：sysfs（通常在 /sys 下装载）下可以提供装载点的设备的路径。路径必须以 / 开头。mount_point：要装载卷的文件系统路径。type：卷上的文件系统类型。如果是外部卡，则通常为 vfat。mnt_flags：Vold 会忽略此字段，应将其设置为 defaultsfs_mgr_flags：Vold 会忽略此字段中不包含 voldmanaged= 标记的统一的 fstab 中的任何行。该标记必须后跟描述卡的标签，以及分区号或字词 auto，例如 voldmanaged=sdcard:auto。其他可能的标记包括 nonremovable、encryptable=sdcard、noemulatedsd 和 encryptable=userdata。
配置详情
框架级别以及更高级别的外部存储空间交互通过 StorageManagerService 来处理。由于 Android 6.0 中进行了配置更改（例如移除了 storage_list.xml 资源叠加层），因此配置详情分成了两类。
Android 5.x 及更低版本
特定于设备的 storage_list.xml 配置文件（通常通过 frameworks/base 叠加层提供）定义存储设备的属性和限制。<StorageList> 元素包含一个或多个 <storage> 元素，其中一个元素应被标记为主元素。<storage> 属性包括：
mountPoint：此装载的文件系统路径。storageDescription：描述此装载的字符串资源。primary：如果此装载是主要外部存储空间，则为 true。removable：如果此装载包含可移动媒体（如实体 SD 卡），则为 true。emulated：如果此装载由可能使用 FUSE 守护进程的内部存储设备模拟和支持，则为 true。mtp-reserve：MTP 应为免费存储预留的存储 MB 数。仅在装载被标记为模拟时使用。allowMassStorage：如果此装载可通过 USB 大容量存储设备共享，则为 true。maxFileSize：文件大小上限（以 MB 为单位）。
设备可以通过模拟由内部存储支持的文件系统（不区分大小写，无需权限）来提供外部存储。system/core/sdcard 中的 FUSE 守护程序提供一个可能的实现，可添加为特定于设备的 init.rc 服务：
# 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 为提供支持的内部存储空间，dest_path 为目标装载点。
配置特定于设备的 init.rc 脚本时，必须将 EXTERNAL_STORAGE 环境变量定义为主要外部存储空间的路径。/sdcard 路径也必须通过符号链接解析到同一位置。如果设备在平台更新之间调整外部存储空间的位置，则应创建符号链接，以便旧的路径继续发挥作用。
Android 6.0
目前，存储子系统的配置集中在特定于设备的 fstab 文件中，并且移除了一些历史静态配置文件/变量，以支持更多动态行为：
storage_list.xml 资源叠加层已被移除，框架已不再使用该叠加层。现在，存储设备在被 vold 检测到时动态配置。
EMULATED_STORAGE_SOURCE/TARGET 环境变量已被移除，Zygote 已不再使用这些变量来配置特定于用户的装载点。相反，用户隔离现在由特定于用户的 GID 强制执行，主要共享存储空间由 vold 在运行时装载到位。
- 开发者可以根据其使用情形继续动态或静态构建路径。在路径中包含 UUID 可识别每个卡，以便为开发者提供更清晰的位置。（例如，
/storage/ABCD-1234/report.txt 明显是与 /storage/DCBA-4321/report.txt 不同的文件。）
- 硬编码的 FUSE 服务已从特定于设备的
init.rc 文件中移除，在需要时将从 vold 动态派生。
除了这些配置更改之外，Android 6.0 还包含可合并的存储设备的概念。对于 Android 6.0 设备，任何未被合并的物理介质都被视为便携式设备。
可合并的存储设备
如需在 fstab 中表示可合并的存储设备，请在 fs_mgr_flags 字段中使用 encryptable=userdata 属性。典型定义如下：
/devices/platform/mtk-msdc.1/mmc_host* auto auto defaults
voldmanaged=sdcard1:auto,encryptable=userdata
合并存储设备时，该平台会擦除内容并写入定义两个分区的 GUID 分区表：
- 一个较小的空
android_meta 分区，预留以备将来使用。分区类型 GUID 为 19A710A2-B3CA-11E4-B026-10604B889DCF。
- 一个较大的
android_ext 分区，使用 dm-crypt 加密并使用 ext4 或 f2fs（取决于内核功能）格式化。分区类型 GUID 为 193D1EA4-B3CA-11E4-B075-10604B889DCF。
便携式存储设备
在 fstab 中，具有 voldmanaged 属性的存储设备默认被视为便携式设备，除非定义了其他属性（如 encryptable=userdata）。例如，典型的 USB OTG 设备的定义如下：
/devices/*/xhci-hcd.0.auto/usb* auto auto defaults
voldmanaged=usb:auto
该平台在装载之前使用 blkid 检测文件系统类型，用户可以选择在文件系统不受支持时将媒体格式化。
本页面上的内容和代码示例受内容许可部分所述许可的限制。Java 和 OpenJDK 是 Oracle 和/或其关联公司的注册商标。
最后更新时间 (UTC)：2025-07-27。
[[["易于理解","easyToUnderstand","thumb-up"],["解决了我的问题","solvedMyProblem","thumb-up"],["其他","otherUp","thumb-up"]],[["没有我需要的信息","missingTheInformationINeed","thumb-down"],["太复杂/步骤太多","tooComplicatedTooManySteps","thumb-down"],["内容需要更新","outOfDate","thumb-down"],["翻译问题","translationIssue","thumb-down"],["示例/代码问题","samplesCodeIssue","thumb-down"],["其他","otherDown","thumb-down"]],["最后更新时间 (UTC)：2025-07-27。"],[],[],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."]]
