< 4th column: Mount options >
The fourth column in
fstab lists all the mount options for the device or partition. This is also the most confusing column in the
file, but knowing what some of the most common options mean, saves you
from a big headache. Yes, there are many options available, but I'll
take a look at the most widely used ones only. For more information,
check out the man page of
auto and noauto With the
auto option, the device will be mounted automatically (at bootup, just like I told you a bit earlier, or when you issue the
mount -a command).
auto is the default option. If you don't want the device to be mounted automatically, use the
noauto option in
noauto, the device can be mounted only explicitly.
user and nouser These are very useful options. The
user option allows normal users to mount the device, whereas
nouser lets only the root to mount the device.
is the default, which is a major cause of headache for new Linux users.
If you're not able to mount your cdrom, floppy, Windows partition, or
something else as a normal user, add the
user option into
exec and noexec
exec lets you execute binaries that are on that partition, whereas
noexec doesn't let you do that.
might be useful for a partition that contains binaries you don't want
to execute on your system, or that can't even be executed on your
system. This might be the case of a Windows partition.
exec is the default option, which is a good thing. Imagine what would happen if you accidentally used the
noexec option with your Linux root partition...
ro Mount the filesystem read-only.
Mount the filesystem read-write. Again, using this option might cure
the headache of many new Linux users who are tearing their hair off
because they can't write to their floppies, Windows partitions, or
sync and async How the input and output to the filesystem should be done.
sync means it's done synchronously. If you look at the example
you'll notice that this is the option used with the floppy. In plain
English, this means that when you, for example, copy a file to the
floppy, the changes are physically written to the floppy at the same time you issue the copy command.
However, if you have the
async option in
input and output is done asynchronously. Now when you copy a file to
the floppy, the changes may be physically written to it long time after
issuing the command. This isn't bad, and may sometimes be favorable,
but can cause some nasty accidents: if you just remove the floppy
without unmounting it first, the copied file may not physically exist
on the floppy yet!
async is the default. However, it may be wise to use
with the floppy, especially if you're used to the way it's done in
Windows and have a tendency to remove floppies before unmounting them
defaults Uses the default options that are rw, suid, dev, exec, auto, nouser, and async.