Be particularly careful when using the -f and -w options together.
When rewriting master database using the -w option, the server requires that the configuration block page size and device size are correct. If you do not provide them on the command line they must agree. The server refits the master device, and puts master and all other included databases back in their proper places.
When you use the -f option to force initialization, your page size and master device size override those in the configuration block. In addition, -f assigns all other unknown spaces—allocation blocks that are either unused or are corrupted—to the master database.