Recipe 9.9. Mounting and Unmounting Removable Disks
9.9.1 Problem
You need to know how to insert and
remove removable disks, such as floppies, CDs, or USB storage
devices.
9.9.2 Solution
Use the mount and umount
commands.
This example mounts a CD drive:
# mount -r -t iso9660 /dev/scd0 /cdrom
-r means read-only; -t
iso9660 is the filesystem type.
/dev/scd0 is the name the kernel assigns to the
device. /cdrom is the directory in which it is
mounted. The /cdrom directory must already be
present before you try to mount the disk.
To find the filesystem type, use the file
command:
$ file - < /dev/scd0
/dev/stdin: ISO 9660 CD-ROM filesystem data 'Data1
You can omit the -r (read-only) flag when
mounting a CD-ROM. It will complain, but it'll mount
the disk anyway:
# mount -t iso9660 /dev/scd0 /cdrom
mount: block device /dev/scd0 is write-protected, mounting read-only
This mounts a floppy disk readable/writable:
# mount -w /dev/fd0 /floppy
The following command mounts a USB storage device. The
noatime option should be used on rewritable
media that have a limited number of rewrites, such as CD/DVD-RW and
flash storage devices:
# mount -w -o noatime /dev/sda1 /memstick
To unmount the device, use:
# umount /memstick
You may get a response like:
# umount /memstick
umount: /memstick: device is busy
This means something (an application, a shell, or a file manager) is
reading the filesystem. You can find out what with
lsof (list open files):
$ lsof /memstick
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
gs 938 dawnm 128r DIR 2,0 1024 12 /memstick/may-04.pdf
bash 938 dawnm 129r DIR 2,0 1024 24 /memstick
Now you can either close out the applications, or kill the lot with a
single command:
# kill -9 `lsof -t /memstick`
mount can only be run by root. To give non-root
users permission to mount removeable disks, you'll
need to edit /etc/fstab (see the next recipe).
9.9.3 Discussion
The umount "device is
busy" error most commonly comes from having a
terminal window open with the mounted device as a current working
directory, like this:
carla@windbag:/floppy$
It is important to unmount a disk before removing it. This gives the
system a chance to complete any writes and to cleanly unmount the
filesystem.
On newer Linux systems, you can get away without specifying the
filesystem type, because mount autodetects the
filesystem types.
9.9.4 See Also
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