You can't. None of the current Red Hat releases support UMSDOS installs. If you have one drive that has one big DOS partition with free space you want to use, you have two options. One is to backup all your DOS data somehow and then repartition the drive into smaller partitions and then restore the DOS data back to a DOS partition. You then have a free partition for linux. The second choice is to use fips. fips is a program that will let you change your partition size of a DOS partition without harming the data on it. It is STRONGLY suggested that you backup your data before using fips. Red Hat Software makes no warranties or claims as to the suitability of using fips for this purpose nor can we guarantee that data will remain unharmed. I haven't heard of anyone having a bad experience with fips, but I won't guarantee it either.