How can I retrieve an SD card's serial number in Android 7.0+?

问题

In some versions of Android, and other variants of Linux, it's possible to get the serial number of a mounted SD card, e.g. by reading the contents of /sys/class/mmc_host/mmc0/mmc0:0001/serial or /sys/block/mmcblk0/device/serial (specific numbers may vary). In my testing this has worked pretty reliably, as long as the SD card is inserted in a built-in SD card slot (not mounted via USB adapter).

But as of Android 7.0 Nougat, the OS is said to be blocking access to this information, at least on some devices. I tested this by running a test app on a new Alcatel A30 GSM (Android 7.0), and in fact the above approach fails with a permission error:

java.io.FileNotFoundException: /sys/block/mmcblk0/device/serial (Permission denied)
at java.io.FileInputStream.open(Native Method)

For future reference, we (testing from an adb shell) have permissions to ls -ld the following:

/sys/class/mmc_host but not /sys/class/mmc_host/mmc0
/sys/block but not /sys/block/mmcblk0

Since the above approach no longer works,

Is there another way to obtain the serial number of a mounted SD card in Android 7.0 or later?
Failing that, is there any documentation or other statement from Google on plans for providing or not providing this function? I haven't found anything in the Android issue tracker, but maybe I'm not searching right.

To make sure the question is clear, I'm talking about what an ordinary (non-system) app running on a non-rooted device can do, with any permissions that an app can normally request and receive.

FYI, the /sbin directory doesn't seem to be readable, so commands like /sbin/udevadm aren't an option.

回答1:

In Android N access to /sys nad /proc was significantly restricted, this was done to provide stricter sandboxes where applications run. This is explained in https://issuetracker.google.com/issues/37091475 as intentional. Actually its not said that all the data in /sys is not accessible, and Google is open to allow access to other files from this location:

If there are specific files in /sys you believe should be available to applications, but are not, please file a new bug where the request can be evaluated. For instance, /sys/devices/system/cpu is available to all processes, so it's inaccurate to say all of /sys is restricted.

I have a bad feeling that google is making changes similar to Apple where it is not allowed to gain hardware id-s. If that is not resolved then the solution is to use google account IDs instead. But I am aware it is not always possible, and will require major changes in business logic (licensing etc.).

Hopefully your bug report will be considered positively.

another related SO I found : File system changes in Android Nougat

回答2:

Use StorageVolume.getUuid() on StorageVolume which you get from StorageManager.

The value is volume ID assigned during formatting of the card, and its length/format differs depending on file system type. For FAT32 it is XXXX-XXXX, for NTFS it's longer hex string, for Internal mass storage it returns null.

回答3:

public String getSDCARDiD()
{
    String sd_cid = null;
    try {

        File file = new File("/sys/block/mmcblk1");
        String memBlk;
        if (file.exists() && file.isDirectory()) {

            memBlk = "mmcblk1";
        } else {
            //System.out.println("not a directory");
            memBlk = "mmcblk0";
        }

        Process cmd = Runtime.getRuntime().exec("cat /sys/block/"+memBlk+"/device/cid");
        BufferedReader br = new BufferedReader(new InputStreamReader(cmd.getInputStream()));
        sd_cid = br.readLine();
        //System.out.println(sd_cid);

    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return sd_cid;
}

try this: reference original link :Android get id of SD Card programmatically

回答4:

adb shell cat /sys/class/mmc_host/mmc1/mmc1:*/cid

You can also try

sudo hwinfo --disk

to get information on your disks, including SD Cards.

Also try

sudo hdparm -I /dev/sdb | more

来源：https://stackoverflow.com/questions/43484564/how-can-i-retrieve-an-sd-cards-serial-number-in-android-7-0

标签

android

sd-card

serial-number