BackupTheDataPartition » History » Revision 7
Revision 6 (Denis 'GNUtoo' Carikli, 10/28/2020 04:53 PM) → Revision 7/39 (Denis 'GNUtoo' Carikli, 10/28/2020 05:07 PM)
h1. How to backup the data partition
{{toc}}
h2. /!\ Warning: Draft
This article is in draft form and is being written:
* Everybody is welcome to contribute
* Some things might not be accurate yet, so beware before using the information contained in it.
Also a big part of this article is copied from [[BackupTheEFS]], it would be better to find a way to include content instead.
h2. What does the data partition contains?
TODO: Point It probably depends on the devices and the Android versions.
On Replicant 6.0, it contains at least the application internal data: When various applications are installed, they have access to some storage where they can read and write data that is only visible to them and not to other applications. This is part of the new article being written Android security model that doesn't trust applications even if they are fully free software.
In addition, on some devices it also contains the users data. This location and external microSD cards is where users typically their files like Music, photos, etc. This data is made accessible to the users in various location through a mechanism called fuse. In Replicant 6, this data is stored in the media directory in the data partition.
Summarry:
| Mount points | Content |
| /data/ | Applications (internal) data |
| /sdcard
/storage/<UUID> | User accessible storage to store music, photos, etc |
Here's where the sdcard user accessible storage comes from:
/sdcard -> /storage/self/primary [1]
/storage/self/primary -> /mnt/user/0/primary [2]
/mnt/user/0/primary -> /storage/emulated/0 [3]
fn1. <pre>root@i9300:/ # readlink /sdcard
/mnt/user/0/primary</pre>
fn2. <pre>root@i9300:/ # readlink /storage/self/primary
/mnt/user/0/primary</pre>
fn3. <pre>root@i9300:/ # readlink /mnt/user/0/primary
/storage/emulated/0</pre>
fn4. <pre>root@i9300:/ # mount | grep "/storage/emulated"
/dev/fuse on /storage/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)</pre>
TODO:
* Explain that the user accessible storage is not always present
* Explain that it depends on the devices (GTA04)
h2. Concerns about it. the application internal data
TODO:
* Explain the issue about the Replicant version <-> application data
h2. Howto
TODO:
* Link to the EFS backup first part
h4. Galaxy S III (GY-I9300)
First, you need to make sure that the data partition is not mounted.
To do that, you can run this command:
<pre>
adb shell "umount -l /data"
</pre>
If the /data partition was mounted, it will unmount it. This will look like that:
<pre>
$ adb shell "umount -l /data"
$
</pre>
If it was not mounted, it will instead show an error that we can ignore:
<pre>
$ adb shell "umount -l /data"
umount: /data: Invalid argument
</pre>
Once this is taken care of, we can backup the partition with the following command:
<pre>
adb pull /dev/block/platform/dw_mmc/by-name/USERDATA ./
</pre>
h2. See also
* The [[BackupsResearch]] page has information on why the backup is done this way. It might also be useful to read and contribute to it if you intend to change the way the backups are done.