Hi;
   I am new to OpenWRT.  I recently purchased and installed a GL-MT300A.  I am able to read from the Micro SD Card.  However, when I try to write to it, it fails due to permissions.  When I access the card it asks for a username and password. How do I set that up?  Using root and rootpswd does not work.  Any help would be appreciated!

Thanks,

Frank

How is the card formatted? 
What FS can you manage (Windows or Linux user)?

Are you using the GL.iNet firmware  or a clean install and the OpenWrt tools?
If the later list all install packages for USB?
If the former what GL.inet version?

Do you need permissions or not?

What is your use case? 
data, DLNA or other?

How is the card formatted?  -- FAT
What FS can you manage (Windows or Linux user)?  --Windows
Are you using the GL.iNet firmware or a clean install and the OpenWrt tools? --GL.iNet firmware
If the later list all install packages for USB?
If the former what GL.inet version?  --OpenWrt Chaos Calmer 15.05 /    LuCI 15.05-50-g02987e9 Release (git-15.322.41240-4e44955)
Do you need permissions or not? -- Do not need permissions (I did not enter a user/pswd from Windows File Explorer)
What is your use case? 
data, DLNA or other? --Data

I did a test with a USB flash drive (mnt/sdb1) and I was able to read and write to it. I also tried again unsuccessfully to write to the internal micro sd card (mnt/mmcblk0p1) and received an error stating access denied and that I needed permission to perform that action (I can read the files without any issues.) From the GL.iNet interface, both share drives show the Windows logo above the drive icon. I am trying to access them from a Windows 10 PC. I did look under GL.iNet interface Advanced Settings-Services-Network Shares and Allow Guests is checked and Read only is not checked for both devices. I also did see that kmod-mmc 3.18.27-1 and kmod-usb-storage 3.18.27-1 are installed.

I have a MIFI and my SD card mounts as mnt/sda1.  Seeing mnt/sdb1 for a USB drive, I assume connected after the card is inserted, would seem to confirm this expectation.  Not sure however if this is the issue.

You can check the logs for sda1, but I think you should post this on the GL.inet forum or contact their tech support.  http://www.gl-inet.com/forums/

You will also want to report your GL.iNet firmware version which you can find on the lower left of the main page.