19.5. Creating and Using CD Media

Contributed by Mike Meyer.

19.5.1. Introduction

CD media provide a number of features that differentiate them from conventional disks. Initially, they were not writable by the user. They are designed so that they can be read continuously without delays to move the head between tracks. They are also much easier to transport between systems.

CD media do have tracks, but this refers to a section of data to be read continuously and not a physical property of the disk. For example, to produce a CD on FreeBSD, prepare the data files that are going to make up the tracks on the CD, then write the tracks to the CD.

The ISO 9660 file system was designed to deal with these differences. To overcome the original file system limits, it provides an extension mechanism that allows properly written CDs to exceed those limits while still working with systems that do not support those extensions.

The sysutils/cdrtools port includes mkisofs(8), a program that can be used to produce a data file containing an ISO 9660 file system. It has options that support various extensions, and is described below.

Which tool to use to burn the CD depends on whether the CD burner is ATAPI or something else. ATAPI CD burners use burncd which is part of the base system. SCSI and USB CD burners should use cdrecord from the sysutils/cdrtools port. It is also possible to use cdrecord and other tools for SCSI drives on ATAPI hardware with the ATAPI/CAM module.

For CD burning software with a graphical user interface, consider X-CD-Roast or K3b. These tools are available as packages or from the sysutils/xcdroast and sysutils/k3b ports. X-CD-Roast and K3b require the ATAPI/CAM module with ATAPI hardware.

19.5.2. mkisofs

The sysutils/cdrtools port also installs mkisofs(8), which produces an ISO 9660 file system that is an image of a directory tree in the UNIX(R) file system name space. The simplest usage is:

# mkisofs -o imagefile.iso /path/to/tree

This command creates an imagefile.iso containing an ISO 9660 file system that is a copy of the tree at /path/to/tree. In the process, it maps the file names to names that fit the limitations of the standard ISO 9660 file system, and will exclude files that have names uncharacteristic of ISO file systems.

A number of options are available to overcome these restrictions. In particular, -R enables the Rock Ridge extensions common to UNIX(R) systems, -J enables Joliet extensions used by Microsoft systems, and -hfs can be used to create HFS file systems used by Mac OS(R).

For CDs that are going to be used only on FreeBSD systems, -U can be used to disable all filename restrictions. When used with -R, it produces a file system image that is identical to the specified FreeBSD tree, though it may violate the ISO 9660 standard in a number of ways.

The last option of general use is -b. This is used to specify the location of the boot image for use in producing an «El Torito» bootable CD. This option takes an argument which is the path to a boot image from the top of the tree being written to the CD. By default, mkisofs(8) creates an ISO image in «floppy disk emulation» mode, and thus expects the boot image to be exactly 1200, 1440 or 2880 KB in size. Some boot loaders, like the one used by the FreeBSD distribution disks, do not use emulation mode. In this case, -no-emul-boot should be used. So, if /tmp/myboot holds a bootable FreeBSD system with the boot image in /tmp/myboot/boot/cdboot, this command would produce the image of an ISO 9660 file system as /tmp/bootable.iso:

# mkisofs -R -no-emul-boot -b boot/cdboot -o /tmp/bootable.iso /tmp/myboot

If md is configured in the kernel, the file system can be mounted as a memory disk with:

# mdconfig -a -t vnode -f /tmp/bootable.iso -u 0
# mount -t cd9660 /dev/md0 /mnt

One can then verify that /mnt and /tmp/myboot are identical.

There are many other options available for mkisofs(8) to fine-tune its behavior. Refer to mkisofs(8) for details.

19.5.3. burncd

For an ATAPI CD burner, burncd can be used to burn an ISO image onto a CD. burncd is part of the base system, installed as /usr/sbin/burncd. Usage is very simple, as it has few options:

# burncd -f cddevice data imagefile.iso fixate

This command will burn a copy of imagefile.iso on cddevice. The default device is /dev/acd0. See burncd(8) for options to set the write speed, eject the CD after burning, and write audio data.

19.5.4. cdrecord

For systems without an ATAPI CD burner, cdrecord can be used to burn CDs. cdrecord is not part of the base system and must be installed from either the sysutils/cdrtools package or port. Changes to the base system can cause binary versions of this program to fail, possibly resulting in a «coaster». It is recommended to either upgrade the port when the system is upgraded, or for users tracking -STABLE, to upgrade the port when a new version becomes available.

While cdrecord has many options, basic usage is simple. Burning an ISO 9660 image is done with:

# cdrecord dev=device imagefile.iso

The tricky part of using cdrecord is finding the dev to use. To find the proper setting, use -scanbus which might produce results like this:

# cdrecord -scanbus
Cdrecord-Clone 2.01 (i386-unknown-freebsd7.0) Copyright (C) 1995-2004 J"org Schilling
Using libscg version 'schily-0.1'
scsibus0:
        0,0,0     0) 'SEAGATE ' 'ST39236LW       ' '0004' Disk
        0,1,0     1) 'SEAGATE ' 'ST39173W        ' '5958' Disk
        0,2,0     2) *
        0,3,0     3) 'iomega  ' 'jaz 1GB         ' 'J.86' Removable Disk
        0,4,0     4) 'NEC     ' 'CD-ROM DRIVE:466' '1.26' Removable CD-ROM
        0,5,0     5) *
        0,6,0     6) *
        0,7,0     7) *
scsibus1:
        1,0,0   100) *
        1,1,0   101) *
        1,2,0   102) *
        1,3,0   103) *
        1,4,0   104) *
        1,5,0   105) 'YAMAHA  ' 'CRW4260         ' '1.0q' Removable CD-ROM
        1,6,0   106) 'ARTEC   ' 'AM12S           ' '1.06' Scanner
        1,7,0   107) *

This lists the appropriate dev value for the devices on the list. Locate the CD burner, and use the three numbers separated by commas as the value for dev. In this case, the CRW device is 1,5,0, so the appropriate input is dev=1,5,0. Refer to cdrecord(1) for easier ways to specify this value and for information on writing audio tracks and controlling the write speed.

19.5.5. Duplicating Audio CDs

To duplicate an audio CD, extract the audio data from the CD to a series of files, then write these files to a blank CD. The process is slightly different for ATAPI and SCSI drives.

Διαδικασία 19.1. SCSI Drives
  1. Use cdda2wav to extract the audio:

    % cdda2wav -vall -D2,0 -B -Owav
  2. Use cdrecord to write the .wav files:

    % cdrecord -v dev=2,0 -dao -useinfo  *.wav

    Make sure that 2,0 is set appropriately, as described in Τμήμα 19.5.4, «cdrecord».

Διαδικασία 19.2. ATAPI Drives

Σημείωση:

With the help of the ATAPI/CAM module, cdda2wav can also be used on ATAPI drives. This tool is usually a better choice for most of users, as it supports jitter correction and endianness, than the method proposed below.

  1. The ATAPI CD driver makes each track available as /dev/acddtnn, where d is the drive number, and nn is the track number written with two decimal digits, prefixed with zero as needed. So the first track on the first disk is /dev/acd0t01, the second is /dev/acd0t02, the third is /dev/acd0t03, and so on.

    Make sure the appropriate files exist in /dev. If the entries are missing, force the system to retaste the media:

    # dd if=/dev/acd0 of=/dev/null count=1
  2. Extract each track using dd(1), making sure to specify a block size when extracting the files:

    # dd if=/dev/acd0t01 of=track1.cdr bs=2352
    # dd if=/dev/acd0t02 of=track2.cdr bs=2352
    ...
  3. Burn the extracted files to disk using burncd. Specify that these are audio files, and that burncd should fixate the disk when finished:

    # burncd -f /dev/acd0 audio track1.cdr track2.cdr ... fixate

19.5.6. Duplicating Data CDs

It is possible to copy a data CD to an image file that is functionally equivalent to the image file created with mkisofs(8), and then use it to duplicate any data CD. The example given here assumes that the CD-ROM device is acd0. Substitute the correct CD-ROM device.

# dd if=/dev/acd0 of=file.iso bs=2048

Now that there is an image, it can be burned to CD as described above.

19.5.7. Using Data CDs

It is possible to mount and read the data on a standard data CD. By default, mount(8) assumes that a file system is of type ufs. Running this command:

# mount /dev/cd0 /mnt

will generate an error about Incorrect super block, and will fail to mount the CD. The CD does not use the UFS file system, so attempts to mount it as such will fail. Instead, tell mount(8) that the file system is of type ISO9660 by specifying -t cd9660 to mount(8). For example, to mount the CD-ROM device, /dev/cd0, under /mnt, use:

# mount -t cd9660 /dev/cd0 /mnt

Replace /dev/cd0 with the device name for the CD device. Also, -t cd9660 executes mount_cd9660(8), meaning the above command is equivalent to:

# mount_cd9660 /dev/cd0 /mnt

While data CD-ROMs from any vendor can be mounted this way, disks with certain ISO 9660 extensions might behave oddly. For example, Joliet disks store all filenames in two-byte Unicode characters. The FreeBSD kernel does not speak Unicode, but the FreeBSD CD9660 driver is able to convert Unicode characters on the fly. If some non-English characters show up as question marks, specify the local charset with -C. For more information, refer to mount_cd9660(8).

Σημείωση:

In order to do this character conversion with the help of -C, the kernel requires the cd9660_iconv.ko module to be loaded. This can be done either by adding this line to loader.conf:

cd9660_iconv_load="YES"

and then rebooting the machine, or by directly loading the module with kldload(8).

Occasionally, Device not configured will be displayed when trying to mount a CD-ROM. This usually means that the CD-ROM drive thinks that there is no disk in the tray, or that the drive is not visible on the bus. It can take a couple of seconds for a CD-ROM drive to realize that a media is present, so be patient.

Sometimes, a SCSI CD-ROM may be missed because it did not have enough time to answer the bus reset. To resolve this, add the following option to the kernel configuration and rebuild the kernel.

options SCSI_DELAY=15000

This tells the SCSI bus to pause 15 seconds during boot, to give the CD-ROM drive every possible chance to answer the bus reset.

19.5.8. Burning Raw Data CDs

It is possible to burn a file directly to CD, without creating an ISO 9660 file system. Some people do this for backup purposes. This command runs more quickly than burning a standard CD:

# burncd -f /dev/acd1 -s 12 data archive.tar.gz fixate

In order to retrieve the data burned to such a CD, the data must be read from the raw device node:

# tar xzvf /dev/acd1

This type of disk can not be mounted as a normal CD-ROM and the data cannot be read under any operating system except FreeBSD. In order to mount the CD, or to share the data with another operating system, mkisofs(8) must be used as described above.

19.5.9. Using the ATAPI/CAM Driver

Contributed by Marc Fonvieille.

This driver allows ATAPI devices, such as CD/DVD drives, to be accessed through the SCSI subsystem, and so allows the use of applications like sysutils/cdrdao or cdrecord(1).

To use this driver, add the following line to /boot/loader.conf:

atapicam_load="YES"

then, reboot the system.

Σημείωση:

Users who prefer to statically compile atapicam(4) support into the kernel, should add this line to the kernel configuration file:

device atapicam

Ensure the following lines are still in the kernel configuration file:

device ata
device scbus
device cd
device pass

Then rebuild, install the new kernel, and reboot the machine.

During the boot process, the burner should show up, like so:

acd0: CD-RW <MATSHITA CD-RW/DVD-ROM UJDA740> at ata1-master PIO4
cd0 at ata1 bus 0 target 0 lun 0
cd0: <MATSHITA CDRW/DVD UJDA740 1.00> Removable CD-ROM SCSI-0 device
cd0: 16.000MB/s transfers
cd0: Attempt to query device size failed: NOT READY, Medium not present - tray closed

The drive can now be accessed via the /dev/cd0 device name. For example, to mount a CD-ROM on /mnt, type the following:

# mount -t cd9660 /dev/cd0 /mnt

As root, run the following command to get the SCSI address of the burner:

# camcontrol devlist
<MATSHITA CDRW/DVD UJDA740 1.00>   at scbus1 target 0 lun 0 (pass0,cd0)

In this example, 1,0,0 is the SCSI address to use with cdrecord(1) and other SCSI applications.

For more information about ATAPI/CAM and SCSI system, refer to atapicam(4) and cam(4).

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