NAME

cmtp - common tape driver

AVAILABILITY

x86

DESCRIPTION

The cmtp device driver is a common interface to various tape devices. (At the time of this release, only SCSI interface tape devices are supported.) The driver supports 1/4" cartridge devices, 4mm digital audio tapes (DAT), 1/2" reel tapes, and 8mm devices. See mtio(7) for details.

The driver can be opened with either the rewind or the no wind on close option. The driver supports a maximum of 128 tape devices. In addition, a maximum of four tape densities per device are supported. The tape density is specified using the different device name suffixes. See mtio(7) for details.

EOT Handling

Most of the tape drives have a logical end of tape (LEOT) before the physical end of tape (PEOT), to guarantee flushing the data onto the tape. The amount of storage between LEOT and PEOT varies from a megabyte to about 20 megabytes, depending on the tape device. Further writing is prohibited to prevent running off the end of the reel.

The first write that encounters EOT will return a short count or zero. The next write will return zero. Further writes to the tape will receive an ENOSPC error.

Reading past EOT is transparent to the user. Reading is only stopped by reading EOFs. For 1/2" reel devices, two consecutive file marks indicate the end of the recorded media.

Ioctls

The behavior of tape positioning ioctls is the same across all supporting devices. However, not all devices support every ioctl. The driver returns an ENOTTY error on unsupported ioctls.

SEE ALSO

cpio(1), mt(1), tar(1), mtio(7)