rhl41.htm

linux的初学电子书

<BR>

<P>After you set the CD-ROM SCSI address properly (the system should recognize the device when the SCSI card boots), the CD-ROM device must be mounted. This can be done manually or embedded in the startup sequence so that the drive is always available.

<BR>

<P>To mount a CD-ROM device, the general command is

<BR>

<BR>

<PRE>

<FONT COLOR="#000080">mount /dev/sr0 /mount_point</FONT></PRE>

<P>where mount_point is a directory that can be used. You must create the directory beforehand in order for the mount to work. For convenience, most systems that use CD-ROMs should create a directory called /cdrom, which is always the mount point.

<BR>

<P>If your CD-ROM doesn't mount properly with this command, the reason might be the disc type or the lack of an entry in the file /etc/fstab which identifies the CD as an ISO 9660 device. The correct syntax to mount an ISO 9660 CD-ROM (also called 
High-Sierra) is

<BR>

<BR>

<PRE>

<FONT COLOR="#000080">mount -t iso9660 /dev/sr0 /mount_point</FONT></PRE>

<P>For this to work correctly, you must have the kernel set to support the ISO 9660 file system. If this hasn't been done, rebuild the kernel with this option added.

<BR>

<P>Linux attempts to lock the CD-ROM drive door when a disc is mounted. This is done to prevent file system confusion due to a media change. Not all CD-ROM drives support door locking, but if you find yourself unable to eject a CD-ROM, it is probably 
because the disc is mounted (it doesn't have to be in use).

<BR>

<BR>

<A NAME="E69E462"></A>

<H4 ALIGN=CENTER>

<CENTER>

<FONT SIZE=4 COLOR="#FF0000"><B>Tape Drives</B></FONT></CENTER></H4>

<BR>

<P>Linux supports several SCSI tape drives. You should check the hardware configuration guide before purchasing one, though, to ensure compatibility. The most popular SCSI tape models, including the Archive Viper QIC drives, Exabyte 8mm drives, and Wangtek 
5150S and DAT tape drives, are all known to work well.

<BR>

<P>SCSI tapes use character device major number 9, and the minor numbers are assigned dynamically. Usually, rewinding tape devices are numbered from 0, so the first tape drive is /dev/rst0 (character mode, major number 9, minor number 0), the second device 
is /dev/rst1 (character mode, major number 9, minor number 1), and so on. Non-rewinding devices have the high bit set in the minor number so that the first non-rewinding tape drive is /dev/nrst0 (character mode, major device 9, minor device 128).

<BR>

<P>The standard naming convention for SCSI tape drives is /dev/nrst{digit} for non-rewinding devices (such as /dev/nrst0, /dev/nrst1, and so on), and /dev/rst{digit} for rewinding devices (such as /dev/rst0 and /dev/rst1).

<BR>

<P>Generally, Linux supports tape devices that use either fixed or variable-length blocks, as long as the block length is smaller than the driver buffer length, which is set to 32KB in most Linux distribution sources (although this can be changed). Tape 
drive parameters such as block size, buffering process, and tape density are set with ioctls, which can be issued by the mt program.

<BR>

<BR>

<A NAME="E69E463"></A>

<H4 ALIGN=CENTER>

<CENTER>

<FONT SIZE=4 COLOR="#FF0000"><B>Other Devices</B></FONT></CENTER></H4>

<BR>

<P>Many other SCSI devices are available, such as scanners, printers, removable cartridge drives, and so on. These are handled by the Linux generic SCSI device driver. The generic SCSI driver provides an interface for sending commands to all SCSI devices.

<BR>

<P>SCSI generic devices use character mode and major number 21. The minor device numbers are assigned dynamically from 0 for the first device, and so on. The generic devices have the names /dev/sg0, /dev/sg1, /dev/sg2, and so on.

<BR>

<BR>

<A NAME="E68E346"></A>

<H3 ALIGN=CENTER>

<CENTER>

<FONT SIZE=5 COLOR="#FF0000"><B>Troubleshooting SCSI Devices</B></FONT></CENTER></H3>

<BR>

<P>Many common problems with SCSI devices are quite easy to solve. Finding the cause of the problem is often the most difficult step. It's usually helpful to read the diagnostic message that the operating system displays when it boots or attempts to use a 
SCSI device.

<BR>

<P>The following are the most common problems encountered with SCSI devices, their probable causes, and possible solutions:

<BR>

<UL>

<UL>

<P>SCSI devices show up at all possible SCSI IDs You have configured the device with the same SCSI address as the controller, which is typically set at SCSI ID 7. Change the jumper settings to another SCSI ID.

<BR>

</UL></UL>

<UL>

<UL>

<P>A SCSI device shows up with all possible LUNs The device probably has bad firmware. The file /usr/src/linux/drivers/scsi/scsi.c contains a list of bad devices under the variable blacklist. You can try adding the device to this list and see if it affects 
the behavior. If not, contact the device manufacturer.

<BR>

</UL></UL>

<UL>

<UL>

<P>Your SCSI system times out Make sure the controller card's interrupts are enabled correctly and that there are no IRQ, DMA, or address conflicts with other boards in your system.

<BR>

</UL></UL>

<UL>

<UL>

<P>You get &quot;sense errors&quot; from error-free devices This is usually caused by either bad cables or improper termination on the chain. Make sure the SCSI chain is terminated at both ends using external or onboard terminators. Don't terminate in the 
middle of the chain, because this can also cause problems. You can probably use passive termination, but for long chains with several devices, try active termination for better behavior.

<BR>

</UL></UL>

<UL>

<UL>

<P>The tape drive is not recognized at boot time Try booting with a tape in the drive.

<BR>

</UL></UL>

<UL>

<UL>

<P>A networking kernel does not work with new SCSI devices The autoprobe routines for many network drivers are not passive and can interfere with some SCSI drivers. Try to disable the network portions to identify the guilty program, and then reconfigure 
it.

<BR>

</UL></UL>

<UL>

<UL>

<P>A SCSI device is detected, but the system is unable to access it You probably don't have a device file for the device. Device drivers should be in /dev and configured with the proper type (block or character) and unique major and minor device numbers. 
Run mkdev for the device.

<BR>

</UL></UL>

<UL>

<UL>

<P>The SCSI controller card fails when it uses memory-mapped I/O This problem is common with Trantor T128 and Seagate boards and is caused when the memory-mapped I/O ports are incorrectly cached. You should have the board's address space marked as 
uncacheable in the XCMOS settings. If you can't mark them as such, disable the cache and see if the board functions properly.

<BR>

</UL></UL>

<UL>

<UL>

<P>Your system fails to find the SCSI devices and you get messages when the system boots, such as scsi : 0 hosts or scsi%d : type: The autoprobe routines on the controller cards rely on the system BIOS autoprobe and can't boot properly. This is 
particularly prevalent with these SCSI adapters: Adaptec 152x, Adaptec 151x, Adaptec AIC-6260, Adaptec AIC-6360, Future Domain 1680, Future Domain TMC-950, Future Domain TMC-8xx, Trantor T128, Trantor T128F, Trantor T228F, Seagate ST01, Seagate ST02, and 
Western Digital 7000. Check that your BIOS is enabled and not conflicting with any other peripheral BIOSes (such as on some adapter cards). If the BIOS is properly enabled, find the board's &quot;signature&quot; by running DOS's DEBUG command to check if 
the board is responding. For example, use the DEBUG command d=c800:0 to see if the board replies with an acknowledgment (assuming you have set the controller card to use address 0xc8000; if not, replace the DEBUG command with the proper address). If the 
card doesn't respond, check the address settings.

<BR>

</UL></UL>

<UL>

<UL>

<P>Sometimes the SCSI system locks up completely There are many possible solutions, including a problem with the host adapter. Check the host adapter with any diagnostics that came with the board. Try a different SCSI cable to see if that is the problem. 
If the lockups seem to occur when multiple devices are in use at the same time, there is probably a firmware problem. Contact the manufacturer to see if upgrades are available that would correct the problem. Finally, check the disk drives to ensure that <A 
NAME="I2"></A>there are no bad blocks that could affect the device files, buffers, or swap space.

<BR>

</UL></UL>

<BR>

<A NAME="E68E347"></A>

<H3 ALIGN=CENTER>

<CENTER>

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

<BR>

<P>SCSI has a reputation for being difficult to work with, but in fact it is one of the easiest and most versatile systems available. Once you get used to the nomenclature, SCSI offers many useful features to the Linux user. Indeed, most veteran UNIX 
people prefer working with SCSI because it is easy to use with the UNIX kernel, and the same applies to Linux.

<P ALIGN=LEFT>

<A HREF="rhl40.htm" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/rhl40.htm" TARGET="_self"><IMG SRC="purprev.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purprev.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Previous Page"></A>

<A HREF="#I0" TARGET="_self"><IMG SRC="purtop.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purtop.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Page Top"></A>

<A HREF="index-1.htm" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/index.htm" TARGET="_self"><IMG SRC="purtoc.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purtoc.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="TOC"></A>

<A HREF="tppmsgs/msgs0.htm#43" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/rhl42.htm" TARGET="_self"><IMG SRC="purnext.gif" tppabs="http://202.113.16.101/%7eeb%7e/Red%20Hat%20Linux%20Unleashed/purnext.gif" WIDTH = 32 HEIGHT = 32 BORDER = 0 ALT="Next Page"></A>


</BODY></HTML>