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4. Floppies, Hard Disks, and the Like

4.1 Managing Devices

You have never thought about it, but the DOS command FORMAT A: does a lot more work than it seems. In fact, when you issue the command FORMAT it will: 1) physically format the disk; 2) create the A:\ directory (= create a filesystem); 3) make the disk available to the user (= mount the disk).

These three steps are addressed separately under Linux. You can use floppies in MS-DOS format, though other formats are available and are better---the MS-DOS format won't let you use long filenames. Here is how to prepare a disk (you'll need to start a session as root):

Now you can extract the disk. Obviously, you have to fdformat and mkfs only unformatted disks, not previously used ones. If you want to use drive B:, refer to fd1H1440 and fd1 instead of fd0H1440 and fd0 in the examples above.

All you used to do with A: or B: is now done using /mnt instead. Examples:


DOS                                     Linux
---------------------------------------------------------------------

C:\GUIDO>dir a:                         $ ls /mnt
C:\GUIDO>copy a:*.*                     $ cp /mnt/* /docs/temp
C:\GUIDO>copy *.zip a:                  $ cp *.zip /mnt/zip
C:\GUIDO>a:                             $ cd /mnt
A:>_                                    /mnt/$ _

Needless to say, what holds for floppies also holds for other devices; for instance, you may want to mount another hard disk or a CD-ROM drive. Here's how to mount the CD-ROM:

# mount -t iso9660 /dev/cdrom /mnt

This was the ``official'' way to mount your disks, but there's a trick in store. Since it's a bit of a nuisance having to be root to mount a floppy or a CD-ROM, every user can be allowed to mount them this way:

Now, to mount a DOS floppy, an ext2 floppy, and a CD-ROM:

$ mount /mnt/a:
$ mount /mnt/a
$ mount /mnt/cdrom

/mnt/a, /mnt/a:, and /mnt/cdrom can now be accessed by every user. I've found that to write on /mnt/a without being root, right after preparing the floppy it's necessary to do:

# mount /mnt/a
# chmod 777 /mnt/a
# umount /mnt/a

Remember that allowing anyone to mount disks this way is a gaping security hole, if you care.

4.2 Backing Up

Now that you know how to handle floppies etc., a couple of lines to see how to do your backup. There are several packages to help you, but the very least you can do for a multi-volume backup is (as root):

# tar -M -cvf /dev/fd0H1440 /dir_to_backup

Make sure to have a formatted floppy in the drive, and several ready. To restore your stuff, insert the first floppy in the drive and do:

# tar -M -xpvf /dev/fd0H1440


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