I have router board version 5.26 on Rb750GL >>> the problem is when i try to paste any thing in files list brings to me this message the pic is attached
close the open file? drag and drop instead of paste?
Your hdd is full, look at the bottom of the window of “file list”. 61.4MB of 61.4MB used.
Clear it up and free the necessary space for the files to be uploaded.
okay sir how I can know the necessary files from the unnecessary files .. and how i can degrade the version to 5.24 I wait your asnwer sir
and also connecting with mac 
You can post in here the file list of your router to have a look at it. Type in terminal
/file print without-paging
copy and paste in here.
To downgrade you just upload the files on the router, and then go to
/system packages downgrade
Hi.
You can try to uninstall some unnecessary packages from /system/packages (and reboot). This will free up some space.
If you have enough space, you can downgrade.
Best wishes: Xen