Tribblix: manual page: tapes.8

TAPES(8) Maintenance Commands and Procedures TAPES(8)

NAME

tapes - creates /dev entries for tape drives attached to the system

SYNOPSIS

/usr/sbin/tapes [-r root_dir]

DESCRIPTION

devfsadm(8) is now the preferred command for /dev and /devices and
should be used instead of tapes.

tapes creates symbolic links in the /dev/rmt directory to the actual
tape device special files under the /devices directory tree. tapes
searches the kernel device tree to see what tape devices are attached
to the system. For each equipped tape drive, the following steps are
performed:

1. The /dev/rmt directory is searched for a /dev/rmt/n entry
that is a symbolic link to the /devices special node of
the current tape drive. If one is found, this determines
the logical controller number of the tape drive.

2. The rest of the special devices associated with the drive
are checked, and incorrect symbolic links are removed and
necessary ones added.

3. If none are found, a new logical controller number is
assigned (the lowest-unused number), and new symbolic
links are created for all the special devices associated
with the drive.

tapes does not remove links to non-existent devices; these must be
removed by hand.

tapes is run each time a reconfiguration-boot is performed, or when
add_drv(8) is executed.

Notice to Driver Writers

tapes(8) considers all devices with the node type DDI_NT_TAPE to be
tape devices; these devices must have their minor name created with a
specific format. The minor name encodes operational modes for the
tape device and consists of an ASCII string of the form [ l,m,h,c,u
][ b ][ n ].

The first character set is used to specify the tape density of the
device, and are named low (l), medium (m), high (h), compressed (c),
and ultra (u). These specifiers only express a relative density; it
is up to the driver to assign specific meanings as needed. For
example, 9 track tape devices interpret these as actual bits-per-inch
densities, where l means 800 BPI, m means 1600 BPI, and h means 6250
BPI, whereas 4mm DAT tapes defines l as standard format, and m, h, c
and u as compressed format. Drivers may choose to implement any or
all of these format types.

During normal tape operation (non-BSD behavior), once an EOF mark has
been reached, subsequent reads from the tape device return an error.
An explicit IOCTL must be issued to space over the EOF mark before
the next file can be read. b instructs the device to observe BSD
behavior, where reading at EOF will cause the tape device to
automatically space over the EOF mark and begin reading from the next
file.

n or no-rewind-on-close instructs the driver to not rewind to the
beginning of tape when the device is closed. Normal behavior for tape
devices is to reposition to BOT when closing. See mtio(4I).

The minor number for tape devices should be created by encoding the
device's instance number using the tape macro MTMINOR and ORing in
the proper combination of density, BSD behavior, and no-rewind flags.
See mtio(4I).

To prevent tapes from attempting to automatically generate links for
a device, drivers must specify a private node type and refrain from
using the node type string DDI_NT_TAPE when calling
ddi_create_minor_node(9F).

OPTIONS

The following options are supported:

-r root_dir
Causes tapes to presume that the /dev/rmt directory
tree is found under root_dir, not directly under /.

ERRORS

If tapes finds entries of a particular logical controller linked to
different physical controllers, it prints an error message and exits
without making any changes to the /dev directory, since it cannot
determine which of the two alternative logical to physical mappings
is correct. The links should be manually corrected or removed before
another reconfiguration boot is performed.

EXAMPLES

Example 1: Creating Tape Device Nodes From Within the Driver's

attach() Function

This example demonstrates creating tape device nodes from within the
xktape driver's attach(9E) function.

#include <sys/mtio.h>
struct tape_minor_info {
char *minor_name;
int minor_mode;
};
/*
* create all combinations of logical tapes
*/
static struct tape_minor_info example_tape[] = {
{"", 0}, /* default tape */
{"l", MT_DENSITY1},
{"lb", MT_DENSITY1 | MT_BSD},
{"lbn", MT_DENSITY1 | MT_BSD | MT_NOREWIND},
{"m", MT_DENSITY2},
{"mb", MT_DENSITY2 | MT_BSD},
{"mbn", MT_DENSITY2 | MT_BSD | MT_NOREWIND},
{"h", MT_DENSITY3},
{"hb", MT_DENSITY3 | MT_BSD},
{"hbn", MT_DENSITY3 | MT_BSD | MT_NOREWIND},
{"c", MT_DENSITY4},
{"cb", MT_DENSITY4 | MT_BSD},
{"cbn", MT_DENSITY4| MT_BSD | MT_NOREWIND},
{NULL, 0},
};

int
xktapeattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
int instance;
struct tape_minor_info *mdp;
/* other stuff in attach... */
instance = ddi_get_instance(dip);

for (mdp = example_tape; mdp->minor_name != NULL; mdp++) {
ddi_create_minor_node(dip, mdp->minor_name, S_IFCHR,
(MTMINOR(instance) | mdp->minor_mode), DDI_NT_TAPE, 0);
}

Installing the xktape driver on a Sun Fire 4800, with the driver
controlling a SCSI tape (target 4 attached to an isp(4D) SCSI HBA)
and performing a reconfiguration-boot creates the following special
files in /devices.

# ls -l /devices/ssm@0,0/pci@18,700000/pci@1/SUNW,isptwo@4
crw-rw-rw- 1 root sys 33,136 Aug 29 00:02 xktape@4,0:
crw-rw-rw- 1 root sys 33,200 Aug 29 00:02 xktape@4,0:b
crw-rw-rw- 1 root sys 33,204 Aug 29 00:02 xktape@4,0:bn
crw-rw-rw- 1 root sys 33,152 Aug 29 00:02 xktape@4,0:c
crw-rw-rw- 1 root sys 33,216 Aug 29 00:02 xktape@4,0:cb
crw-rw-rw- 1 root sys 33,220 Aug 29 00:02 xktape@4,0:cbn
crw-rw-rw- 1 root sys 33,156 Aug 29 00:02 xktape@4,0:cn
crw-rw-rw- 1 root sys 33,144 Aug 29 00:02 xktape@4,0:h
crw-rw-rw- 1 root sys 33,208 Aug 29 00:02 xktape@4,0:hb
crw-rw-rw- 1 root sys 33,212 Aug 29 00:02 xktape@4,0:hbn
crw-rw-rw- 1 root sys 33,148 Aug 29 00:02 xktape@4,0:hn
crw-rw-rw- 1 root sys 33,128 Aug 29 00:02 xktape@4,0:l
crw-rw-rw- 1 root sys 33,192 Aug 29 00:02 xktape@4,0:lb
crw-rw-rw- 1 root sys 33,196 Aug 29 00:02 xktape@4,0:lbn
crw-rw-rw- 1 root sys 33,132 Aug 29 00:02 xktape@4,0:ln
crw-rw-rw- 1 root sys 33,136 Aug 29 00:02 xktape@4,0:m
crw-rw-rw- 1 root sys 33,200 Aug 29 00:02 xktape@4,0:mb
crw-rw-rw- 1 root sys 33,204 Aug 29 00:02 xktape@4,0:mbn
crw-rw-rw- 1 root sys 33,140 Aug 29 00:02 xktape@4,0:mn
crw-rw-rw- 1 root sys 33,140 Aug 29 00:02 xktape@4,0:n

/dev/rmt will contain the logical tape devices (symbolic links to
tape devices in /devices).

# ls -l /dev/rmt
/dev/rmt/0 -> ../../devices/[....]/xktape@4,0:
/dev/rmt/0b -> ../../devices/[....]/xktape@4,0:b
/dev/rmt/0bn -> ../../devices/[....]/xktape@4,0:bn
/dev/rmt/0c -> ../../devices/[....]/xktape@4,0:c
/dev/rmt/0cb -> ../../devices/[....]/xktape@4,0:cb
/dev/rmt/0cbn -> ../../devices/[....]/xktape@4,0:cbn
/dev/rmt/0cn -> ../../devices/[....]/xktape@4,0:cn
/dev/rmt/0h -> ../../devices/[....]/xktape@4,0:h
/dev/rmt/0hb -> ../../devices/[....]/xktape@4,0:hb
/dev/rmt/0hbn -> ../../devices/[....]/xktape@4,0:hbn
/dev/rmt/0hn -> ../../devices/[....]/xktape@4,0:hn
/dev/rmt/0l -> ../../devices/[....]/xktape@4,0:l
/dev/rmt/0lb -> ../../devices/[....]/xktape@4,0:lb
/dev/rmt/0lbn -> ../../devices/[....]/xktape@4,0:lbn
/dev/rmt/0ln -> ../../devices/[....]/xktape@4,0:ln
/dev/rmt/0m -> ../../devices/[....]/xktape@4,0:m
/dev/rmt/0mb -> ../../devices/[....]/xktape@4,0:mb
/dev/rmt/0mbn -> ../../devices/[....]/xktape@4,0:mbn
/dev/rmt/0mn -> ../../devices/[....]/xktape@4,0:mn
/dev/rmt/0n -> ../../devices/[....]/xktape@4,0:n

FILES

/dev/rmt/*
logical tape devices

/devices/*
tape device nodes

BUGS

tapes silently ignores malformed minor device names.

February 17, 2023 TAPES(8)