Writing CD-Rs

Creating an ISO-9660 image; Burning the CD-R; Copying CD-ROMs;

Under FreeBSD, data on conventional hard disks is stored in the UNIX File System or UFS format. CD-ROMs and CD-Rs use a different file system, the ISO 9660 format, which is compatible with other systems. This is not a problem when you mount a CD-ROM: FreeBSD includes a read-only ISO 9660 file system When you want to write a CD-R, however, things are a little more complicated: the medium requires you to write the entire file system at once, and since the file system is stored in a different format, you can't just copy the UFS file system Instead, you must first create an image of the file system that you want to put on the CD-R, and then you copy it. We'll look at these steps in more detail below.

Creating an ISO-9660 image

The first step is to create the ISO 9660 file system image, frequently simply called an ISO image. There are a number of ports available in the Ports Collection; here we'll look at mkisof s, which is part of the cdrtools port. Installation isn't quite as straightforward as you might expect: you need a special fag to install mkisof s:

# cd /usr/ports/sysutils/cdrtools

# make install -DMKISOFS

mkisof s has a bewildering number of parameters. Here are the important ones:

• The -A option specifies the application ID, a text string written to the header of the file system to describe the "application" on the image. It can be up to 128 characters long.
• Use -b if you want to be able to boot from the CD, such as a FreeBSD bootable CD. In the case of FreeBSD, use the 2.88 MB image fbppies/boot.lp which is built as part of the release process. Note that this file must be in one of the directories included in the image, and the name is relative to the root directory of the CD.
• The -f option tells mkisofs to follow symbolic links. If you don't specify this option and you have symbolic links in the directory from which you create the image, the resultant CD-ROM image will contain only a symbolic link instead of the file itself. If the file to which the symbolic link points is below the top-level (root) directory, this is the preferred way to do things, because it saves space, but if it points outside the CD-ROM, the file will not appear on the CD-ROM at all Use this option if you have symbolic links to files outside the directory that you're using for the root of the CD-ROM file system.
• The - J option makes the CD compatible with Microsoft's Joliet format. You don't need it for FreeBSD, but it doesn't cost much, so it's a good idea to include it if there's a chance the CD will be used in a Microsoft environment.
• Use the -o option to specify the name of the resultant ISO image. This image is the size of the resultant CD, so it could be up to 700 MB.
• The -p option specifies the preparer ID, another ISO 9660 header field to specify who made the CD-ROM.
• The - r option specifies the Rock Ridge Extensions that are used to store UNIX file names. It makes a number of assumptions about permissions and owners; see the man page for details. It takes no parameters.
• The -T option tells mkisofs to include a translation file TRANS.TBL in each directory for use by systems that don't support the Rock Ridge extensions. For each file name in the directory, TRANS.TBL contains a Microsoft-compatible name (up to eight characters, a period (.) and up to three more characters). The names bear a slight resemblance to the original names.
• If you don't like the name TRANS.TBL, you can specify a different name with the -table-name option, which inplies -T. For example, if you write -table-name.MAP you will generate names that won't show up with a normal ]s command.
• The -V option specifies the volume ID for the file system This will normally be more specific than the application ID; for example, each CD in a set of CDs might have the same application ID and a different volume ID.
• The final parameters are the names of the directories that will be included in the image. You can specify multiple directories. In each case, the entire directory hierarchy will be included.

This is a lot of stuff to type in every time. It's easier to write a Make file and use make:

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APPLID = 'Dummy application"

BOOT =

#To make it bootable, put in something like this:

#Note that the -b option is there as well

#BOOT = "-b floppies/bootflp "

ISO = /var/tmp/isoimage

PREPARER = "me"

VOLID = 'Volume 0000" DIR = .

cdronr

mkisofs -A${APPLID} ${BOOT} -J -o ${ISO} -f -p ${PREPARER} -r -T -V ${VOLID} ${DIR}

For example, to make a bootable CD-R of the FreeBSD release, you would first perform the make world and make release. Assuming that the release directory is /home/release, you will find the directory trees for the first two CD-ROMs in /home/re-lease/R/cdrom/discl and /home/release/R/cdrom/disc2. You could do this: # make cdrom DIR=/home/release/R/cdrom/discl

mkisofs -A 'Dummy application " -J -o ../iso -table-name .MAP -p "Greg Lehe -V 'Volume 000"

6.40% done, estimate finish Sun Aug 27 13:34:54 2000
12.79% done, estimate finish Sun Aug 27 13:35:02 2000
19.19% done, estimate finish Sun Aug 27 13:35:05 2000
25.57% done, estimate finish Sun Aug 27 13:35:10 2000
31.97% done, estimate finish Sun Aug 27 13:35:10 2000
38.36% done, estimate finish Sun Aug 27 13:35:10 2000
44.75% done, estimate finish Sun Aug 27 13:35:10 2000
51.15% done, estimate finish Sun Aug 27 13:35:12 2000
57.54% done, estimate finish Sun Aug 27 13:35:12 2000
63.94% done, estimate finish Sun Aug 27 13:35:12 2000
70.34% done, estimate finish Sun Aug 27 13:35:11 2000
76.72% done, estimate finish Sun Aug 27 13:35:13 2000
83.12% done, estimate finish Sun Aug 27 13:35:12 2000
89.52% done, estimate finish Sun Aug 27 13:35:13 2000
95.90% done, estimate finish Sun Aug 27 13:35:13 2000

Total translation table size: 35119

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Total rockridge attributes bytes: 59724

Total directory bytes: 104448

Path table size(bytes): 256

Max brk space used 86224

78211 extents written (152 Mb)

The progress reports are rather boring nowadays, considering that the whole process only takes a couple of minutes, but the summary information at the bottom can be of interest.

Testing the CD-R

So now you have an ISO image. How do you know it's correct? It's just a single file, and it could have just about anything on it. You can burn a CD, of course, but if it's junk, you have another coaster. If you're not sure, it's better to look inside first. You can do that by using it as the basis for an md vnode device.

The md driver creates a number of different kinds of pseudo-device. See the man page md (4) for more details. We use the vnode device, a special file that refers to file system files. Support for md is included in the GENERIC kernel, but if you've built a kernel without the md driver, you can load it as a kid. If you're not sure, try loading the kid anyway. Then you associate a vnode device with the ISO image iso-image using the program mdconfig:

# kidload md load the kid module if necessary

kidload: can't load md: File exists already loaded or in the kernel

# mdconfig -a -t vnode -f iso-image configure the device

mdO this is the name assigned

# mount -t cd9660 /dev/mdO /mnt mount it

After this, you will be able to access the image at /mnt as a normal file system. Don't forget to un mount and un configure the file when you're finished:

# umount /mnt

# mdconfig -d -u 0

Older releases of FreeBSD used the vn driver, which used different syntax.

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Burning the CD-R

Once you have created and tested an ISO image, you can copy it to CD-R. For SCSI burners, you use cdrecord; AIA (IDE) CD-R burners you use burned. In the following sections we'll look at both programs.

Burning a CD-R on an ATA burner

To bum a CD-R in an AIA (or IDE) burner, use burned, which is part of the base system. Typically you'll only have one CD-R burner on the system, so it will be called /dev/acdO. You'll have something like this in your dmesg output:

acdO: CD-RW at atal-slave BIOSPIO

burned has both fags and commands. For our purposes, the most important fags are:

• The - f device option specifies the device to use for the burning process.
• The -m option tells burned to close the disk in multi session mode.
• The -q option tells burned to be quiet and not to print progress messages. In fact, it's not very verbose anyway.
• The - s speed option specifies the speed of the burner device. It defaults to 1, so you'H save a lot of time using this.
• The -t option specifies a test write: burned does not actually write on the medium.
• The -v (verbose) option prints a few extra progress messages.

The most important commands for writing ISO 9660 CD-ROMs are:

• data or model write data tracks, also known as model tracks, for the image files named on the command line.
• fixate fixates the medium by generating the table of contents. This should be the last command to burned.

If burned doesn't recognize a command, it assumes it's a file name. If it does, it assumes it isn't a file name. This can be confusing: there are other commands not mentioned in the list above, for example raw. If you have an ISO file called raw,

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you‘H have to rename it before you can bum it with burned.

Before you start, you should decide on the recording speed. If your machine is fast enough, use the rated recording speed. In the case of the example machine, that's an 8x speed (Le. it records at eight times the speed at which a normal audio CD is played). Before you do this, though, you should make sure that your system can keep a sufficient data rate so that there is always data available to transfer to the CD-R. If it can't keep up, you'll get an underrun, a gap in the data, and your CD-R is worthless (a coaster).

To make sure you don't make coasters, you should do a test run. The system goes through all the motions, but it doesn't actually write anything to the CD-R blank. Nevertheless, it tests all aspects of the bum, so you must have a valid CD-R blank in the drive, otherwise the attempt will fail To test bum an image called iso, enter:

# burned -f/dev/acdOc -t -v -s 8 data iso fixate

adding type 0x08 file iso size 184576 KB 92288 blocks

next writeable LBA 0

addr = 0 size = 189005824 blocks = 92288

writing from file iso size 184576 KB

written this track 6880 KB (3%) total 6880 KB

At this point, burned overwrites the line with progress indications until it is find. Finally, you see:

written this track 184576 KB (100%) total 184576 KB fixating CD, please wait..

burned: ioctl(CDRIOCFIXATE): Input/output error

This last line appears a little alarming. It's not really serious, though: the CD has not really been written, so it's not possible to read from it. A number of CD-R drives return error conditions under these circumstances.

If everything was OK in the test run, you can repeat the command without the -1 fag:

# burned -f/dev/acdOc -v -s 8 data iso fixate

The output is identical, but this time you should not get the error message.

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Burning a CD-R on a SCSI burner

If you have a SCSI burner, use cdrecord, which is part of the cdrtools port we installed on page 243. cdrecord has a rather strange habit of not using device names: instead, it accesses the device directly by its SCSI parameters (bus, unit and LUN). You can get these parameters from the dmesg output in /var/run/dmesg.boot, but there's an easier way:

# cdrecord -scanbus

Using libscg version 'schily-0.1'

scsibusO:

0,0,0 0) 'MATSHITA' 'CD-R CW-7503 ' '1.06' Removable CD-ROM cdrecord: Warning: controller returns zero sized CD capabilities page, cdrecord: Warning: controller returns wrong size for CD capabilities page, cdrecord: Warning: controller returns wrong page 0 for CD capabilities page (2A
0,1,0 1) ‘IEAC ' 'CD-ROM CD-532S "1.0А Removable CD-ROM
0,2,0 2) *
0,3,0 3) *
0,4,0 4) 'SONY ' 'SDT-10000 ”0101' Removable Tape
0,5,0 5) *
0,6,0 6) *
0,7,0 7) *
0,8,0 8) 'QUANTUM' 'QM318000TD-SW ’ 'N491' Disk

This output doesn't tell you exactly which devices are CD-Rs, and it also doesn't look at any except the first SCSI bus. Alternatively, you can use the standard system utility camcontrol:

at scbusO target 0 lun 0 (passO,cd( at scbusO target 1 lun 0 (passl,cdl at scbusO target 4 lun 0 (sa0,pass2) at scbusO target 8 lun 0 (pass at scbusl target 1 lun 0 (sal,

at scbusl target 3 lun 0 (sa2,pass5) at scbusl target 4 lun 0 (sa3,pass6) at scbusl target 6 lun 0 (pass7,cd2) at scbusl target 6 lun 1 (pass8,cd3)

scbusl scbusl scbusl

scbusl scbusl

target target target target target

lun lun lun lun lun

2
3
4
5
6
(pass9,cd4)
(passl0,cd5)
(passll,cd6)
(passl2,cd7)
(passl3,cd8)

Either way, you need to recognize the CD-R device, which in this case is relatively easy: it's the Matsushita CW-7503 ('MATSHITA ") at the very beginning of each list, cdrecord refers to this device as 0,0,0 (bus 0, target 0, LUN 0).

The next thing to look at is the recording speed. If your machine is fast enough, use the rated recording speed. In the case of the example machine, that's an 8x speed (le. it records at 8 times the speed at which a normal audio CD is played). Before you do this, though, you should make sure that your system can keep a sufficient data rate so that there is always data available when to go on the CD. If you can't keep up, you'll get an underrun, a gap in the data, and your CD-R is worthless (a coaster).

To make sure you don't make coasters, you should do a dummy run. The system goes through all the motions, but it doesn't actually write anything to the CD-R blank. Nevertheless, it tests all aspects of the bum, so you must have a valid CD-R blank in the drive, otherwise the attempt will fail To burn an image called iso, enter:

# cdrecord -dummy -v dev=0,0,0 -speed=8 iso

TOC Type: 1 = CD-ROM

scsidev: '0,0,0'

scsibus: 0 target: 0 lun: 0

Using libscg version 'schily-0.1'

atapi: 0

Device type : Removable CD-ROM

Version : 2

Response Format: 2

Capabilities : SYNC LINKED

VendorJnfo : 'MATSHFIA'

Identifikation : 'CD-R CW-7503 '

Revision : '1.06'

Device seems to be: Generic mmc CD-R.

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Using generic SCSI-3/mmc CD-R driver (mmc_cdr).

Driver flags : SWABAUDIO

FIFO size : 4194304 = 4096 KB

Track 01: data 152 MB

Total size: 175 MB (17:22.84) = 78213 sectors

Lout start: 175 MB (17:24/63) = 78213 sectors

Current Secsize: 2048 АПР info from disk:

Indicated writing power: 5

Is not unrestricted

Is not erasable

АПР start of lead in: -11080(97:34/20)

АПР start of lead out: 335100 (74:30/00)

Disk type: Long strategy type (Cyanine, AZO or similar) Manuf. index: 11 Manufacturer: Mitsubishi Chemical Corporation

Blocks total: 335100 Blocks current: 335100 Blocks remaining: 256887

RBlocks total: 342460 RBlocks current: 342460 RBlocks remaining: 264247

Starting to write CD/DVD at speed 8 in dummy mode for single session.

Last chance to quit, starting dummy write in 1 seconds.

Waiting for reader process to fill input buffer ... input buffer ready.

Starting new track at sector: 0

Track 01:0 of 152 MB written (fifo 100%).

At this point, cdrecord overwrites the last line with progress indications until it is finished. If you're watching, keep an eye on the fifo information at the end of the line. This gives you an idea how well the system is keeping up with the burner. Il the utilization drops to 0, you will get an underrun, and the blank would have become a coaster if this were for real

Finally, you see:

Track 01:152 of 152 MB written (fifo 100%).

Track 01: Total bytes read/written: 160176128/160176128 (78211 sectors).

Writing time: 136.918s

Fixating...

WARNING: Some drives don't like fixation in dummy mode. Fixating time: 35.9( cdrecord: fifo had 2523 puts and 2523 gets.

cdrecord: fifo was 0 times empty and 2451 times full, min fill was 96%.

The summary information at the end shows that at some point the fifo dropped

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below 100% full, but this is far from being a problem. If, on the other hand, there was a lot of disk activity at the same time, you might find the fifo level dropping much lower.

When you're sure that you won't have any problems, you can do the real thing: just repeat the command without the -dummy option. The output looks almost identical

Copying CD-ROMs

Frequently you'll want to make a verbatim copy of another CD. There are copyright implications here, of course, but many CD-ROMs are not restricted. In particular, you may make copies of FreeBSD CD-ROMs for your personal use.

CD-ROMs are already in ISO format, of course, so to get a file /iso, as in the examples above, you could just perform a literal copy with dd:

# dd il=/dev/cdOc of=iso bs=128k

The bs=12 8k tells dd to copy in blocks of 128 кВ. It's not strictly necessary, but if you omit it, it will perform a separate transfer for every sector, and on a slow machine it can be much less efficient.

There's an even easier way, though, if you have two CD-ROM drives: you can frequently copy directly from one drive to the other, without storing on disk at all To do this, of course, you need to be very sure that your CD-ROM drive is fast enough. In particular, if it spins down during the copy, you will almost certainly have underruns and a useless copy. Be very sure to do a dummy run first. Let's assume that your second CD-ROM drive is /dev/cdlc (a SCSI drive). For IDE drives, write:

# burned -f/dev/acdOc -t -v -s 8 data /dev/cdlc fixate

In this example, the -f option indicates that /dev/acdOc is the (IDE) CD-R burner, /dev/cdlc is the (SCSI) CD-ROM drive with the original CD-ROM. You don't need to mount /dev/cdlc, since it's being accessed as raw data, not a file system

When you're sure this will work, remove the -1 tag and repeat. For SCSI, enter

# cdrecord -dummy -v dev=0,0,0 -speed=8 /dev/cdlc

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