/etc/fstab: Automating the mount process

The file /etc/fstab (it stands for "file system table") contains descriptions of filesystems that you mount often. These filesystems can then be mounted with a shorter command, such as mount /cdrom. You can also configure filesystems to mount automatically when the system boots. You'll probably want to mount all of your hard disk filesystems when you boot.

Look at this file now, by typing more /etc/fstab. It will have two or more entries that were configured automatically when you installed the system. It probably looks something like this:

     # /etc/fstab: static file system information.
    #
    #                
    /dev/hda1            /               ext2    defaults    0       1
    /dev/hda3            none            swap    sw          0       0
    proc                 /proc           proc    defaults    0       0
  
    /dev/hda5            /tmp            ext2    defaults    0       2
    /dev/hda6            /home           ext2    defaults    0       2
    /dev/hda7            /usr            ext2    defaults    0       2
  
    /dev/hdc             /cdrom          iso9660 ro          0       0
    /dev/fd0             /floppy         auto    noauto,sync 0       0

The first column lists the device the filesystem resides on. The second lists the mount point, the third the filesystem type. The line beginning proc is a special filesystem explained in The proc filesystem, Section 4.8.3. Notice that the swap partition (/dev/hda3 in the example) has no mount point, so the mount point column contains none.

The last three columns may require some explanation.

The fifth column is used by the dump utility to decide when to back up the filesystem. FIXME: cross ref to dump

The sixth column is used by fsck to decide in what order to check filesystems when you boot the system. The root filesystem should have a 1 in this field, filesystems which don't need to be checked (such as the swap partition) should have a 0, and all other filesystems should have a 2. FIXME: cross ref to fsck, also, is the swap partition really a filesystem?

Column four contains one or more options to use when mounting the filesystem. Here's a brief summary (some of these probably won't make much sense yet - they're here for future reference):

async and sync

Do I/O synchronously or asynchronously. Synchronous I/O writes changes to files immediately, while asynchronous I/O may keep data in buffers and write it later, for efficiency reasons. FIXME: cross ref to section on sync for full explanation. Also, should recommend when to choose one or the other.

ro and rw

Mount the filesystem read-only or read-write. If you don't need to make any changes to the filesystem, it's a good idea to mount it read-only so you don't accidentally mess something up. Also, read-only devices (such as CD-ROM drives and floppy disks with write protection tabs) should be mounted read-only.

auto and noauto

When the system boots, or whenever you type mount -a, mount tries to mount all the filesystems listed in /etc/fstab. If you don't want it to automatically mount a filesystem, you should use the noauto option. It's probably a good idea to use noauto with removable media such as floppy disks, because there may or may not be a disk in the drive. You'll want to mount these filesystems manually after you put in a disk.

dev and nodev

Use or ignore device files on this filesystem. You might use nodev if you mount the root directory of another system on your system - you don't want your system to try to use the devices on the other system.

user and nouser

Permit or forbid ordinary users to mount the filesystem. nouser means that only root can mount the filesystem. This is the normal arrangement. You might use the user option to access the floppy drive without having to be root.

exec and noexec

Allow or do not allow the execution of files on this filesystem. Probably you won't need these options.

suid and nosuid

Allow or do not allow the suid bit to take effect. Probably you won't need these options. See Making files suid/sgid, Section 4.8.4.2.

defaults

Equivalent to: rw, dev, suid, exec, auto, nouser, async. You can specify defaults followed by other options to override specific aspects of defaults.

See Basic partitioning for more information

ls /dev/disk/by-label -lah

ls /dev/disk/by-id -lah

ls /dev/disk/by-uuid -lah

1. /mnt Typically used for fixed hard drives HD/SCSI.
2. /media Typically used for removable media (CD/DVD/USB/Zip).

1. /mnt/windows
2. /mnt/data
3. /media/usb

sudo mkdir /media/usb

To mount an iso image (*.iso NOT CD/DVD device):

Code:

sudo mount -t iso9660 -o ro,loop=/dev/loop0