[Motorola Droid RAZR] Ohmster:
RO = Read Only

RW = Read/Write

Welder, before you "have to read one of Ohmster's books again", the short answer is that Stargo is aware of it, I asked him about it, his reply was:

This should not be necessary as media_rw is way too broad. sdcard_rw should be enough. Looking into it...

...so you can skip the rest if it is too much to read. Sorry, I am not a man of few words. :(

Stargo DID say that <group gid="sdcard_rw" /> should be enough, implying the extra line would be redundant. And that he was looking into it.

The file I want to modify or "add a line to" is a system file. Okay, this phone is rooted, I have a root enabled File Manager, ES File Explorer, and a text editor with Pro Root Key purchased. That should be all I need to find and open the file, add the new permission line, save the file, and see the results. But I can't. The save file operation fails.

Permissions for the file are: -rw-r--r-- owner, root. Meaning the owner of the file, root, can read and write this file, i.e.: as root I can read, change, and save it. The groups can only read it, the world can only read it. But even as root, I cannot save the modified file and it is not the file permission stopping me, it is the entire file system is mounted as RO or "Read Only". As long as cm11 is running, I cannot write to that file. I even tried manually doing it in a terminal window and using vi, a crude text editor, to open the file and found it was RO. Not going to happen.

The file is /system/etc/permissions/platform.xml. Finding the section: WRITE_EXTERNAL_STORAGE shows two entries. A screenshot was requested of the modified file, and what was added to that section is:

<group gid="media_rw" />

Really, go see the link below to the post.

Before we get too far out there, peek at what this is all about, HERE. This "Fix" that allows the camera, pictures, videos, music, to use the Ext SD Card. It was written for a Galaxy S3 phone, other phones may apply, but not tested.

The guy had 75 Thanks for this post from those who were helped by it.

The fix is for Kit Kat 4.4 roms, which have severely cut the permissions to use the Ext SD Card. THAT I believe. I *always* saved pictures, video, and music to EXT SD because I nave like "no room" internal. Since Kit Kat 4.4, no apps can write files there, or at least not most. I did set Titanium Backup to keep backups on Ext SD and that works fine. Besides, none of the apps ask you were you want to save files or give option to Ext SD Card, e.g.: Google Music, Camera, Camcorder, anything. They write where they want and it is always Internal SD Card. (Where i have no space available.)

I looked at my phone, have the same file and it does not have the modification, so I want to add it, reboot, and see if the video or other cameras will now write to Ext SD. Can't do it with RO permissions on the file system, even for root. I asked Stargo about it. He believes the permissions set in platform.xml are sufficient and this line should not be needed, else it would be present in ALL our phones. It is. What he told me is:

"You have to mount the filesystem read/write before trying to edit the file"

Gave me instruction code on how to do it:

mount -oremount,rw /system

THAT makes me nervous. I have computer experience and never have I unmounted a Linux system disk while the system was in operation. It would fail or horribly crash the system. To do something like that in Linux (Which is the parent of Android.) I would run the computer on a rescue CD, then use tools to modify the file that is now no longer in use or mounted on a live file system.

UN-mounting the system file system while in use is NOT something I would ever try.

Perhaps vie ADB over a USB cable when the phone is NOT running CM11 or a patch to flash that would write the modified file over the existing one before the phone boots. This is developer stuff, I cannot do it. Since Micheal now knows about it, if it were significant, I am sure he will put it into an update. I cannot go any further with it.

Hope this clears things up. :)