Saturday, March 10, 2012

SDCard write problem fix for Samsung Galaxy Tab 7.7 GT-P6800

There are those of you who know the experience. You went out and got yourself a Samsung Galaxy Tab 7.7. You then promptly bought and loaded in a 32GB micro-SDHC memory card. You then install a third-party file explorer or zip manager app. Perhaps it is Astro File Manager, or Androzip, or ES File EXplorer, or my personal all-time favorite for both desktop and mobile, Total Commander. You find that you can read files from your SD card but you always get an error when you try to do a write operation, whether it's copy or move in, delete, or create a new directory. But somehow it works fine if you use the default file explorer. Which you have given up on because, well, it doesn't offer you what you want. Or you just plain don't like the look of it.

This is more of an issue with the default permission settings in the Android 3.2 Honeycomb OS than it is an issue with the tablet hardware itself, or your particular SDHC card. This has been known to occur across different tablet models as well, from the Galaxy Tab series to the Motorola Xoom, even to some of the cheap Chinese Android tablets out there. It is 100% a software problem. So no worries about the hardware here. And it doesn't occur on the Galaxy S2 or Galaxy Note which are generally running Android 2.3.6 Gingerbread.

Turns out Google had for some reason since Honeycomb 3.2 decided to split the write permissions for the internal memory (the path of which is confusingly named /mnt/sdcard) and external SD card memory (the path being /mnt/sdcard/extStorages/SdCard) into WRITE_EXTERNAL_STORAGE and WRITE_MEDIA_STORAGE respectively.

Before Honeycomb 3.2, apps only had to request for the permission WRITE_EXTERNAL_STORAGE and they would have write access to both the internal and external so-called "sdcard" sets of memory. Now, apps have to request for WRITE_MEDIA_STORAGE if they want to write to the external SD card, but many of them have not yet been updated to do so yet. This affects file managers / explorer / compression utility type apps most often because users would tend to use them to copy / move / zip files within the file system.
Security theory aside, what's the easiest way to fix this? First off, your Galaxy Tab 7.7 needs to be rooted and CWM Recovery needs to be installed. If you're not already there, take a look at the tutorial on how to root the Samsung Galaxy Tab 7.7 which also includes the instructions to install CWM Recovery as well.

Next,download the file fix_perms_20120205.zip to your tablet. You can do this via a copy/paste into the Card folder while your tablet is connected by USB, or if you're reading this on your tablet, you can just download it directly into /mnt/sdcard/extStorages/SdCard. Do not unzip the file. Just leave it as a zip file.

Finally and here is where you have to do the same thing as when you were trying to do the initial root. Unplug the USB cable (if it is connected) and turn off the tablet (hold down the Power button and select Power Off). Turn on the tablet in recovery mode - hold down both the Power and Volume Up buttons until the tablet turns on, and keep both buttons pressed until the recovery screen comes up. Using the Volume Up, Volume Down and Power buttons, go to install update from external storage, and point it to the file fix_perms_20120205.zip that you had put in earlier. Reboot when done.

Once rebooted, your apps should now have full write access to the external SD card memory. Actually what is happening is that when your apps request for WRITE_EXTERNAL_STORAGE, this patch adds the WRITE_MEDIA_STORAGE permission as well, so your file explorer / compression apps will now work as you would expect. You can read up the XDA links in the references if you want the full details of the SDCard write saga or if you would like to know how to accomplish this by yourself manually.

Indications are this method should work for the other Samsung Galaxy Tab series of tablets as well, such as the Tab 7.0 Plus, 8.9 and 10.1, or even the Motorola Xoom or other models, so long as they are also rooted and have CWM Recovery, but hey don't quote me, I have not tried this method on all these other models. Hence the references are all provided below and if you have one of the other Honeycomb 3.2 devices, you can judge for yourself whether you might want to carry this out on your own.

As for Ice Cream Sandwich, it is not yet known whether this bug or ah, "feature" will remain, but latest reports are that, yes, they are going to continue with this separate permission model. Hopefully in the future, more apps would have been amended to include the necessary permission/security settings but in the meantime, users would probably have to continue using workarounds such as this.


References :

1. How to root the Samsung Galaxy Tab 7.7 GT-P6800
2. [FAQ] Common Issues with the P6800 and their Solutions
3. [FIX] Fix external SD Card permissions
4. Writing to external SD guide

3 comments:

Thanks a lot for this post. Solved the problem. Had to slightly amend the process in the end, in CWM I couldn't see the fix zip file in „apply update from SD card“, so I had to put it in the internal SD card folder and then use „install zip from internal SD“ option in CWM. But it worked just the same. Thanks again.

In my case (ICS), I got an error "E:signature verification failed" instead :( Any help?

Also got a "E:signature verification failed" message. Any solutions?

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