This section presents commands that work with
devices. You'll learn how to mount and unmount devices and how
to format a floppy diskette.
You cannot access a hard drive partition, CD-ROM,
or floppy diskette until the related device or
partition is
mounted. Mounting a device checks the status of
the device and readies it for access. Linux can be
configured to automatically mount a device or partition when
it boots; but you must manually mount other devices and
partitions.
If a device uses removable media, the media may not be
present when the system boots. If the system is configured
to automatically mount such a device and the media is not
present, an error occurs. Therefore, devices that use
removable media are not generally configured for automatic
mounting.
Before you can remove media from a device, you must
unmount it. The system also unmounts devices when it shuts
down. Mounting and unmounting devices is a privileged
operation; generally, only the root user can manually mount
and unmount devices.
To mount a device or partition, you use the
mount command, which has the following
pattern:
mount
options device directory
The
mount command provides many
options. However, you can generally use the
mount command without any options;
consult the manual page to learn about the available
options.
The reason you can use the
mount
command without options is that the file
/etc/fstab describes your system's
devices and the type of filesystem each is likely to
contain. If you add a new device to your system, you may
need to revise the contents of
/etc/fstab or specify appropriate
options when you mount the device.
You must specify the device that you want to mount and a
directory, known as the
mount point. To
make it convenient to access various devices, Linux treats a
mounted device as a directory; mounting the device
associates it with the named directory. For example, a
common operation is mounting a CD-ROM. You can
accomplish this with the command:
root@desktop:/root#
mount /dev/cdrom /cdrom
The file
/dev/cdrom is a link that
points to the actual device file associated with your
system's CD-ROM drive. The directory
/cdrom is a directory created by
the install program; this directory is conventionally used
as the mounting point for CD-ROMs. After the
command has completed, you can access files and directories
on the CD-ROM just as you would access ordinary
files and directories on the path
/cdrom. For example, to list the
top-level files and directories of the CD-ROM simply
type:
root@desktop:/root#
ls /cdrom
To mount a floppy diskette in your
a: drive, type:
root@desktop:/root#
mount /dev/fd0 /floppy
To unmount a device, specify its mount point as an
argument of the
umount command. For
example, to unmount a CD-ROM diskette, type:
root@desktop:/root#
umount /cdrom
Only the root user can unmount a device. Moreover, a
device can be unmounted only if it's not in use. If, for
example, the working directory of a user is a directory of
the device, the device cannot be unmounted.
If you can't unmount a device, check each virtual
console to see if one of them has a session that's using
the device as its working directory. If so, either exit
the session or change to a working directory that isn't
associated with the device.
Before you can write data on a floppy diskette, you must
format it. The Linux command to format a floppy is
fdformat. Simply follow the command with
an argument that specifies the floppy drive and the capacity
of the diskette; the available arguments are listed in
Table 4.6. For example, to format a 1.44 MB
floppy in your system's a: drive, type:
root@desktop:/root#
fdformat /dev/fd0H1440
Once you've formatted the floppy, you can mount it and
then read and write it. Be sure you unmount the floppy
diskette before you remove it. Unmounting the floppy
diskette ensures that all pending data has been written to
it; otherwise, the floppy diskette may be unusable due to
corrupt data.
Table 4.6: Floppy Drive Designators
|
Designation |
Meaning |
|
/dev/fd0 |
3.5-inch diskette
in
a: (1.44 MB) |
|
/dev/fd0d360 |
5.25-inch
diskette in
a: (360 kB) |
|
/dev/fd0D720 |
3.5-inch diskette
in
a: (720 kB) |
|
/dev/fd0h1200 |
5.25-inch
diskette in
a: (1.2 MB) |
|
/dev/fd0H1440 |
3.5-inch diskette
in
a: (1.44 MB) |
|
/dev/fd0H2880 |
3.5-inch diskette
in
a: (2.88 MB) |
|
/dev/fd1 |
3.5-inch diskette
in
b: (1.44 MB) |
|
/dev/fd1d360 |
5.25-inch
diskette in
b: (360 kB) |
|
/dev/fd1D720 |
3.5-inch diskette
in
b: (720 kB) |
|
/dev/fd1h1200 |
5.25-inch
diskette in
b: (1.2 MB) |
|
/dev/fd1H1440 |
3.5-inch diskette
in
b: (1.44 MB) |
|
/dev/fd1H2880 |
3.5-inch diskette
in
b: (2.88 MB) |
