Android 11 & 12 write access to /vendor file system

[eric_bentley]

I create Android images for our dev kit (imx8qxp) for Android versions 9-12.  I create the mek_8q userdebug-eng lunch target image.  

Under Android versions 9/10, I can disable verity and remount the fs to have write access to the /vendor fs.  (I specifically need access to /vendor/etc sub directories).  Under Android 11/12, even though I've disabled verity and performed adb remount (tried mount -o rw,remount /vendor as well), I continue to find the file system is read only: "Read-only file system")

How can I make /vendor write-able?

Here is my current mounting of /vendor:

mek_8q:/vendor/etc/bluetooth # touch foo
touch: 'foo': Read-only file system
1|mek_8q:/vendor/etc/bluetooth # mount | grep vendor
/dev/block/dm-1 on /vendor type ext4 (ro,seclabel,noatime,errors=panic,inode_readahead_blks=8)
overlay on /vendor type overlay (rw,seclabel,noatime,lowerdir=/vendor,upperdir=/mnt/scratch/overlay/vendor/upper,workdir=/mnt/scratch/overlay/vendor/work,override_creds=off)
overlay on /vendor/etc type overlay (ro,seclabel,relatime,lowerdir=/vendor/vendor_overlay_soc/imx8qxp/vendor/etc:/vendor/etc,override_creds=off)

Thanks!

[Zhiming_Liu]

Hi @eric_bentley 

Please refer this part:

https://www.nxp.com/docs/en/user-guide/ANDROID_USERS_GUIDE.pdf

[eric_bentley]

I was able to unmount and remount the overlay rw by supplying work and upper directories.

I was also able to prevent the issue by removing the creation of the overlay via mod to init.rc.