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8.2.1: Read only support for ftape-2.x

Except when using the driver in `raw' mode -- i.e. after issuing the MTIOCFTMODE ioctl (see MTIOCFTMODE) or when using the driver with the raw devices `/dev/(n)rawft*' -- the driver detects tapes that were already used by the original ftape-2.x driver and the sftape driver from pre-3.04 ftape distributions, i.e. tapes that have the `Linux raw format V*' label written to the header segments(1).

The driver then switches to read-only mode to prevent the recorded data to be overwritten. This is necessary even if the tape is not full because ftape-4.05 uses the third segment on tape for a volume table, according to the QIC-113 standard (QIC organisations home page).

Thus allowing write access to tapes already used by the original ftape-2.x or sftape could result in the damage of the data of the first segment and therefore I imagined it a good idea to disable write access to those tapes. This over-write protection is ignored when the tape is positioned at begin of tape (referred to as BOT) in which case the tape label and the original file marks are silently overwritten.


(1) The first 58 kilobytes of a tape cartridge are used to store status information about the tape cartridge and are referred to as header segments.


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