Using mounted DOS filesystems

In addition to using the DOS utilities, you can mount a DOS filesystem and access its files directly while still operating from the SCO OpenServer system. A general description of mounting filesystems is given in ``Mounting a filesystem''.

This means that you can edit DOS files in place, without first copying them into the UNIX filesystem. The SCO OpenServer system deals with DOS files by superimposing certain qualities of UNIX filesystems over the DOS filesystem without changing the actual files. UNIX filesystems are highly structured and operate in a multiuser environment. In order to make DOS files readily accessible, access permissions and file ownership are superimposed on the DOS filesystem when mounted.

The major restriction with mounting a DOS floppy or a DOS partition is that DOS applications (for example, your DOS word processing package) cannot be executed under this arrangement.

If you need to use your DOS applications, you (or your system administrator) need to do one of the following:

• Boot the system as a DOS system (only your system administrator can do this).

• Make the DOS partition the active partition, so that the computer boots DOS by default (only your system administrator can do this).

• Run SCO® Merge^(TM) from the UNIX partition. (Ask your system administrator if you have this application on your system.)

DOS utilities cannot be used on a mounted DOS filesystem. Normally, only your system administrator can mount a filesystem. Access by users is governed by the permissions and ownership that your system administrator places on the DOS filesystem. The system administrator must either mount the DOS filesystem or set up the system so that users can use the
mnt(C) command. The filesystem must also be mountable. Such systems have an entry in /etc/default/filesys that contains the command mount=yes. See ``Mounting a filesystem'' for details of /etc/default/filesys and how to check its contents.

Because of the limitations discussed earlier, DOS does not recognize permissions or ownership. When mounted from the UNIX partition, DOS files behave as follows:

• The permissions and ownership of the filesystem are governed by the mount point. For example, if root creates a mount point /X with permissions of 777, all users can read or write the contents of the filesystem. If root creates a mount point with permissions of 700, only root can read or write the contents of the filesystem.

• The ownership of regular files is governed by the mount point. If the mount point is owned by root, all files within the DOS filesystem and any created by other users are all owned by root.

• DOS does not distinguish between users, therefore files can be either readable/writable for everyone, or read-only for everyone. The permissions for regular files are either 0777 for readable/writable files or 0555 for read-only files. When a file is created, the permissions are based on the umask of the creator, but may not be the same as they would be in a normal filesystem. If the umask allows anyone to write to the file, then the permissions are set to 777; if no one can write to the file, the permissions are set to 555. See umask(C) for details.