Backing Up In Linux

Want to start backing up your Linux system properly, but don't know what's available to do the job? Yusuf Nagree helps you configure and use available backup hardware.

There are currently three main types of tape drives available for the PC (and hence Linux). There are those based on SCSI interfaces, those based on the floppy drive interface (QIC-40, QIC-80, QIC-117, QIC-3010 and QIC-3020), and QIC-02 type drives. A new breed of tape drives that attach to the IDE interface is coming, but at the moment, Linux support is minimal. There is no Linux support for drives that attach to the parallel port.

You cannot simply attach a tape drive to your machine and expect Linux to automatically recognize it. You need to tell the kernel about it, and this can involve recompiling the kernel. In addition, you need entries in your /dev directory so that programs under Linux can access the tape drives.

Below, I will describe how to set up the two most common types of tape drives.

Floppy Interface Tape Drives

Tape drives that connect to the floppy drive interface have the advantage that no separate interface card is required; they are, therefore, fairly cheap and reliable. Thus, this breed of tape drive has been very popular.

One of the first tape drives of this type was the Colorado Jumbo 250. The tape drive cable for these drives attaches to the floppy drive interface. The QIC-80 specification defines how to access these tape drives. Many other tape drives, including the Iomega 250, Conner C250MQ, Wangtek 304, and Colorado Jumbo 350 are QIC-80 compatible.

Tape drives that use the QIC-80 specification require a program (actually, a “Loadable Kernel Module”) called ftape, written by Bas Laarhoven and Kai Harrekilde-Petersen, which at the time of writing is at version 2.03b. QIC-117 and QIC-40 formats are also supported by ftape, as is QIC-3010 and QIC-3020 (i.e. QIC-WIDE) in an experimental form. A complete list of tape drives supported by ftape can be found in the vndors.h file in the ftape source distribution. Support for some enhanced controller boards is also provided—specifically Iomega Tape Accelerator, Colorado FC-10, and Mountain MACH-2. Support for the FC-15 and FC-20 high speed Colorado controller boards is not yet provided.

Most Linux distributions include ftape; if yours doesn't, you will have to download it (see Tape Resources sidebar). Unless you are using module version support in your kernel (if you don't understand what this means, you can assume that you are not using it), ftape will need to be recompiled each time you update your kernel.

Compiling ftape

First, go to your source directory and unpack the sources:

:$ cd /usr/local/src
$ tar xzf ftape-2.03b.tar.gz

You will end up with a directory ftape-2.03b; all the ftape source files will be in this directory along with some documentation files. You now need to compile ftape to end up with a file ftape.o:

$ cd ftape-2.03b
$ make clean
$ make dep
$ make all

Next, you need to make sure that your kernel has been compiled with ftape support built in. Recompiling the kernel is beyond the scope of this article (see the Kernel-HOWTO more details), but basically, do:

$ cd /usr/src/linux
$ make config

to accept all the default values for all options (unless, of course, you do want to change them), and when you get to the QIC-117 option, answer Y. Leave the NR_FTAPE_BUFFERS at the default value of 3. Then recompile the kernel (usually make clean dep; make zImage) and install the new kernel. Don't forget to re-run lilo if you use it.

If you are using very recent kernels (1.3.30 and above), you will have to use zftape. zftape (written by Claus Heine) is based on ftape but provides support for the dynamically loaded buffers provided by the later kernels. You compile it exactly the same way as ftape. Installing it is also done the same way as with ftape, except that you will use the name zftape instead of ftape. When configuring your kernel, you will not get asked any questions about QIC-117 options or NR_FTAPE_BUFFERS.

Even if you are not using recent kernels, zftape provides some very good enhancements over the basic ftape package, including software compression, and it is well worthwhile upgrading to get it.

Making The Devices

Next, you need to make sure that the /dev entries have been created correctly for ftape. Once again, if you have a Linux distribution, this will more than likely have been done, otherwise; you will have to create them manually. Do:

$ ls /dev/*rft* /dev/*tape*

and you should have at least the following files:

/dev/rft0
/dev/nrft0
/dev/ftape
/dev/nftape

If you do not, create them (you will have to be root):

$ mknod -m 666 /dev/rft0 c 27 0
$ mknod -m 666 /dev/nrft0 c 27 4
$ ln -s /dev/rft0 /dev/ftape
$ ln -s /dev/nrft0 /dev/nftape

Alternatively, if you have a script called MAKEDEV in your /dev/ directory, you can simply run this to have your devices created correctly.

$ cd /dev
$ ./MAKEDEV ftape

If you are using the zftape package, there are certain other device names that you will require. They can be created from the zftape Makefile by:

$ make mknod
$ ln -s /dev/rft0 /dev/ftape
$ ln -s /dev/nrft0 /dev/nftape
$ ln -s /dev/qft0 /dev/qftape
$ ln -s /dev/nqft0 /dev/nqftape
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