Dual boot stopped and it's my fault!
Patience is a virtue. You're gonna need to remember this by the time I finish.
Computer: Mac book pro mid 2010, replaced the HD and partitioned.
Half for 10.6 mac os formatted extended journal, half Ubuntu 16 formatted in fat32 .
10.6 boots and then load Ubuntu. Both working , just had to get a driver loaded for wifi in Ubuntu..
Switched back and forth for several days and getting addicted to Ubuntu.
While in Ubuntu, inserted a usb with files from another mac using 10.11.
Could read and copy but could not write to it, no permission.
I cannot recall how many commands I entered trying to change permission based on info from the forum.
My last attempt was to boot into 10.6 and change to disable journaling on the usb then boot into Ubuntu.
No change EXCEPT I cannot boot into 10.6 now.
I know I did it, I just don't know what I did.
I have to reiterate, I do not remember all the commands I entered, but there were many.
Can I dig out of the mess I created?
I can get into a grub prompt from the Ubuntu start up if that helps.