lsg09.htm

linux-unix130.linux.and.unix.ebooks130 linux and unix ebookslinuxLearning Linux - Collection of 12 E

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<LI>The frequency with which the filesystem needs to be dumped by the dump command. If no value is given, a zero is assumed, and dump doesn't dump the filesystem. Most versions of Linux do not support this option (including the version supplied with this book).



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<LI>A number indicating which order the filesystems should be checked at reboot time by fsck. A root filesystem should have a value of 1, and other filesystems can have higher values. If a filesystem is mounted within the root fileystem, it is checked in order. If a value of zero is present, fsck ignores the drive. Many versions of Linux do not support this option.



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<P>If you plan on using a single CD-ROM disc frequently (such as the Linux distribution CD or a disk of utilities), mounting the CD-ROM drive by using /etc/fstab is handy. Modify the fstab file as shown previously, substituting your device device name and mount points.



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<P>The mount and umount commands are usually executed only by root. To allow users to mount and unmount CD-ROM drives, you must modify the entry in the /etc/fstab file. Change the entry to read



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<FONT COLOR="#000080">/dev/scd0 /cdrom iso9660 user,noauto,ro 1 1</FONT></PRE>



<P>The new options on the CD-ROM line allow any user to mount and unmount the drive. The noauto option tells Linux not to mount the filesystem when it first boots, which allows users to change and mount CD-ROMs without worrying about the initial filesystem state. Change the device driver name to match your device name. Alternatively, some utilities allow users to mount and unmount CD-ROM drives without requiring modification to the /etc/fstab file. One, called usermount, is popular and only allows access to CD-ROMs (not other devices), which is useful.



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<FONT SIZE=5 COLOR="#FF0000"><B>Playing Audio CD-ROMs</B></FONT></CENTER></H3>



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<P>If you want to play an audio-only CD on your CD-ROM drive, you must unmount the filesystem (see the previous section) and have an application capable of playing the disc. Linux includes a number of CD applications, some command-line based and some for the X Window interface. You can get a lot more information about these applications from the documentation that came with your Linux distribution set or from the application's files.



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<P>The basic audio CD application supplied with Linux is Workman, which runs under X and lets you move through the audio disc with an on-screen control panel that looks just like a CD player's controls. A character-based version of the program is called WorkBone. Several other applications, such as cdtool, Xmcd, cdplayer, and xcdplayer are also available. More programs are released on FTP and BBS sites regularly, expanding the features supported. Some CD-ROM drives require special versions of the audio CD software, so check the documentation carefully.



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<FONT SIZE=5 COLOR="#FF0000"><B>Using PhotoCDs with Linux</B></FONT></CENTER></H3>



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<P>If you want to use Kodak's PhotoCD format to view photographs and other images on your Linux system, you need to obtain a PhotoCD utility. Note that not all CD-ROM drives support PhotoCD formats.



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<P>The primary PhotoCD utility for Linux is called hpcdtoppm, which converts PhotoCD files to pixmap format. These files can then be displayed using any viewing tool or even saved as use for background for your X session. The photocd utility is similar and can also convert PhotoCD files to Targa and Windows bitmap formats. The utility xpcd, written by the same author as photocd, allows you to examine thumbnail views of pictures stored on a PhotoCD and load them at different resolutions. You can also select specific areas of an image to convert or examine.



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<FONT SIZE=5 COLOR="#FF0000"><B>Troubleshooting the CD-ROM Drive</B></FONT></CENTER></H3>



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<P>If you have installed a CD-ROM drive and configured it properly, yet you still cannot read from the disk, there are a number of potential solutions. Sometimes the problem is simple&#151;you forgot to mount the drive or misspelled its name. Unless you specifically know the problem, try these solutions in the order that they are presented to isolate the problem's root cause.



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<FONT SIZE=4 COLOR="#FF0000"><B>Check the Kernel</B></FONT></CENTER></H4>



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<P>Check that the kernel has been relinked and rebuilt with the new CD-ROM device drivers added. You can check the date of the kernel build with the command



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<FONT COLOR="#000080">uname -a</FONT></PRE>



<P>If the date doesn't correspond to the date of your linking and rebuilding, the build wasn't completed properly and the CD-ROM drivers are missing. Rebuild the kernel.



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<P>Alternatively, you can look at a list of the drivers that are compiled into the kernel by looking at the file /proc/devices. This file lists all the devices, as in the following example:



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<FONT COLOR="#000080">Character devices:



 1 mem



 4 ttyp



 5 cua



 6 lp



 7 vcs



10 mouse



Block devices:



 2 fd



 8 sd



11 sr</FONT></PRE>



<P>In this example, the device number 11 refers to the SCSI CD-ROM drive. If you linked in a kernel for a Matsushita CD-ROM, for example, there would be a line in the file that looks like the following:



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<FONT COLOR="#000080">25 sbpcd</FONT></PRE>



<P>The numbers in the first column are the major device numbers; the second column has the device driver initials. Check the device numbers you created and compare them to this file. If the major device number is not listed, the CD-ROM driver is not linked to the kernel. Rebuild the kernel.



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<FONT SIZE=4 COLOR="#FF0000"><B>Check the Device</B></FONT></CENTER></H4>



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<P>If the device drivers are linked into the kernel and the CD-ROM device has been mounted but you can't see anything on the disk, try the following command and watch the light on the CD-ROM faceplate that indicates drive activity:



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<FONT COLOR="#000080">dd if=/dev/cdrom of=/dev/null bs=2048



^C</FONT></PRE>



<P>Substitute the name of the CD-ROM device if it is not linked to /dev/cdrom. This command tries to copy the contents of the CD-ROM to /dev/null. After issuing the command, issue a Ctrl+C to interrupt it, as the command doesn't really do anything useful. If the drive indicator light blinked or stayed on for a while, yet you still can't read anything on the disk, the disc in the drive is probably not an ISO 9660 filesystem format, or it is ISO 9660 format, but you forgot to link in the ISO 9660 drivers.



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<P>Verify that the ISO 9660 drivers are active by examining the contents of the /proc/filesystems file. You should see this line under the nodev section:



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<FONT COLOR="#000080">iso9660</FONT></PRE>



<P>If this line doesn't show up in the file, the ISO 9660 device driver is not linked to the kernel. Relink the kernel with this option.



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<P>If the ISO 9660 driver is linked in and shows up in the /proc/filesystem file, check that when you mount the CD-ROM drive you specify the option



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<FONT COLOR="#000080">-t iso9660</FONT></PRE>



<P>on the command line.



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<P>If you are specifying the ISO 9660 driver and it is linked in to the kernel, chances are the CD is not ISO 9660 format. Try another disc and hope for better results.



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<FONT SIZE=4 COLOR="#FF0000"><B>Check the Drive Settings</B></FONT></CENTER></H4>



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<P>If you are having problems with a proprietary CD-ROM drive, chances are the settings for the interface are not correct. The settings are usually defined in a file with the name of the device, such as sbpcd.h for a Matsushita drive. The location of the file varies, so use a wildcard find routine to locate it:



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<FONT COLOR="#000080">find / -name sbpcd* -print</FONT></PRE>



<P>When you find the file, which usually has a .h extension (such as sbpcd.h), check the contents to ensure that the I/O address, DMA, and IRQ (if applicable) match your card's settings. If you can't find a configuration file, check the settings of the card manually. There may be a conflict with the I/O address, DMA, or IRQ and another device on your system.



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<FONT SIZE=4 COLOR="#FF0000"><B>Device Busy Errors</B></FONT></CENTER></H4>



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<P>If you get device busy errors, and you are running a SCSI system, you may have assigned the CD-ROM device a SCSI ID the same as another device. Check the SCSI IDs.



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<P>If you get the device busy message when you try to unmount a CD-ROM drive, then a process is using the drive and is preventing the CD-ROM drive from unmounting successfully. Make sure you are not currently in the CD-ROM directory structure when you try to unmount it. If you can't find the suspect process, use the command



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<FONT COLOR="#000080">fuser -v /cdrom</FONT></PRE>



<P>to display the processes currently using the device (change the name of the mount point if necessary to match your system).



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<FONT SIZE=5 COLOR="#FF0000"><B>Summary</B></FONT></CENTER></H3>



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<P>Despite the amount of information presented in this chapter, adding a CD-ROM drive to your system and properly configuring it can take less than 15 minutes. Unfortunately, the wide variety of proprietary CD-ROM drives means that there will always be a few that are not mentioned in the Linux documentation and will require varying degrees of extra work to properly configure. If you can, stick to one of the major brands that you know is supported. CD-ROMs make a Linux user's life much easier by offering large libraries of utilities and distribution software, and a CD-ROM drive is definitely worth adding to most systems.



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