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6.2: Kerneld

zftape can be used with the kerneld daemon safely. The driver simply locks itself in memory under the following conditions:

Most of the above module locking situations can be cleared by simply rewinding the tape device when it isn't needed any more. However, please remember that this is not the case when the tape block size has been changed using MTSETBLK. In this case one has to restore the default block size of 10k:

mt -f /dev/nqft0 10240

Other situations might require to send a MTRESET command to the driver, especially if a tape operation has been interrupted before completion. Think for example of removing the tape cartridge during a formatting procedure. The MTRESET command has the same effect (or should have) as re-inserting the tape cartridge and opening the tape device (see MTRESET).

The following is an example of what could happen when the driver would not lock itself in memory:

claus@anaxagoras:claus$ mt -f /dev/nqft0 eom claus@anaxagoras:claus$ sleep 120 claus@anaxagoras:claus$ tar -cvvf /dev/nqft0 /usr/src/ftape-3.04d

When ftape would be unloaded in between this would result in erasing the entire cartridge and then writing the new volume starting at BOT but as ftape is not unloaded this does not result in erasing the entire cartridge.

Keep in mind that the ftape driver is quite large. Compiling the driver with full debugging support and loading ftape and zftape consumes roughly 250kb (including the 3 dma buffer the driver needs for the data transfer) so it might be a good idea to not keep it constantly in memory.

Please refer also to the documentation included in the `modules' (or `modutils') package on how to configure the modules utilities for use with the kerneld program (see Requirements). There is a short example how to modify /etc/conf.modules for use with ftape. See Insmod ftape.


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