Do you know why some canning sites tell you not to can cabbage, unless I miss read, but my Kerr canning book says cabbage can be pressured canned?
I did a bit of research on this question. I checked a couple of extension websites and my Ball Blue Book of Preserving.
I could not find any safety information on canning cabbage. I must assume that it is not recommended.
The methods I do see where cabbage being safely canned is making sauerkraut or a pickled product. The vinegar or pickling ads the acid that cabbage needs to be safe for canning.
Edited to add:
It does seem that though I have no experience canning cabbage... others have had success with it. Read the comments for more information.