After much trial and error I have it working. Here is the line I added to fstab:
//192.168.1.42/mysql_backup /media/mysql_backup cifs guest,uid=1000,gid-1000 0 0
I gather that some user/pass has to be specified or you need to specify guest. The uid & gid I used are my user on Ubuntu. Without specifying that it was mounted with root user and group which kept me from being able to write to files. I don't understand why it mounted as root rather than the current user/group or even the user/group already assigned to the files and dirs on the server. This is something I still don;t understand about Linux.
One problem. When I boot Ubuntu I see a quick message about CIFS error. It's too quick to read it all. When I run grep cifs /var/log/syslog I see the following:
Nov 15 14:44:13 Ubuntu-VM kernel: [ 4.170545] CIFS VFS: cifs_mount failed w/return code = -101
Nov 15 14:44:13 Ubuntu-VM kernel: [ 4.419017] CIFS VFS: cifs_mount failed w/return code = -101
I haven't created any other mounts in my fstab so I can only assume those messages are related to this mount, but it seems to be working correctly. How do I figure out what those errors are related to?