1.\" Copyright (c) 2008, Sun Microsystems, Inc. All Rights Reserved 2.\" Copyright 2018, Joyent, Inc. 3.\" The contents of this file are subject to the terms of the 4.\" Common Development and Distribution License (the "License"). 5.\" You may not use this file except in compliance with the License. 6.\" 7.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 8.\" or http://www.opensolaris.org/os/licensing. 9.\" See the License for the specific language governing permissions 10.\" and limitations under the License. 11.\" 12.\" When distributing Covered Code, include this CDDL HEADER in each 13.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE. 14.\" If applicable, add the following below this CDDL HEADER, with the 15.\" fields enclosed by brackets "[]" replaced with your own identifying 16.\" information: Portions Copyright [yyyy] [name of copyright owner] 17.Dd March 13, 2022 18.Dt MTIO 4I 19.Os 20.Sh NAME 21.Nm mtio 22.Nd general magnetic tape interface 23.Sh SYNOPSIS 24.In sys/types.h 25.In sys/ioctl.h 26.In sys/mtio.h 27.Sh DESCRIPTION 281/2", 1/4", 4mm, and 8mm magnetic tape drives all share the same general 29character device interface. 30.Pp 31There are two types of tape records: data records and end-of-file (EOF) 32records. 33.Sy EOF 34records are also known as tape marks and file marks. 35A record is separated by interrecord (or tape) gaps on a tape. 36.Pp 37End-of-recorded-media (EOM) is indicated by two 38.Sy EOF 39marks on 1/2\(dq tape; by one 40.Sy EOF 41mark on 1/4\(dq, 4mm, and 8mm cartridge tapes. 42.Ss "1/2\(dq Reel Tape" 43Data bytes are recorded in parallel onto the 9-track tape. 44Since it is a 45variable-length tape device, the number of bytes in a physical record may vary. 46.Pp 47The recording formats available (check specific tape drive) are 800 48.Sy BPI , 491600 50.Sy BPI , 516250 52.Sy BPI , 53and data compression. 54Actual storage capacity is a function of the recording format and the length of the tape reel. 55For example, using a 2400 foot tape, 20 Mbyte can be stored using 800 56.Sy BPI , 5740 Mbyte using 1600 58.Sy BPI , 59140 Mbyte using 6250 60.Sy BPI , 61or up to 700 Mbyte using data compression. 62.Ss "1/4\(dq Cartridge Tape" 63Data is recorded serially onto 1/4\(dq cartridge tape. 64The number of bytes per 65record is determined by the physical record size of the device. 66The I/O request 67size must be a multiple of the physical record size of the device. 68For 69.Sy QIC-11 , 70.Sy QIC-24 , 71and 72.Sy QIC-150 73tape drives, the block size is 512 bytes. 74.Pp 75The records are recorded on tracks in a serpentine motion. 76As one track is 77completed, the drive switches to the next and begins writing in the opposite 78direction, eliminating the wasted motion of rewinding. 79Each file, including the last, ends with one file mark. 80.Pp 81Storage capacity is based on the number of tracks the drive is capable of 82recording. 83For example, 4-track drives can only record 20 Mbyte of data on a 84450 foot tape; 9-track drives can record up to 45 Mbyte of data on a tape of 85the same length. 86.Sy QIC-11 87is the only tape format available for 4-track 88tape drives. 89In contrast, 9-track tape drives can use either 90.Sy QIC-24 91or 92.Sy QIC-11 . 93Storage capacity is not appreciably affected by using either format. 94.Sy QIC-24 95is preferable to 96.Sy QIC-11 97because it records a 98reference signal to mark the position of the first track on the tape, and each 99block has a unique block number. 100.Pp 101The 102.Sy QIC-150 103tape drives require 104.Sy DC-6150 105(or equivalent) tape cartridges for writing. 106However, they can read other tape cartridges in 107.Sy QIC-11 , 108.Sy QIC-24 , 109or 110.Sy QIC-120 111tape formats. 112.Ss "8mm Cartridge Tape" 113Data is recorded serially onto 8mm helical scan cartridge tape. 114Since it is a 115variable-length tape device, the number of bytes in a physical record may 116vary. 117The recording formats available (check specific tape drive) are standard 1182Gbyte, 5Gbyte, and compressed format. 119.Ss "4mm DAT Tape" 120Data is recorded either in Digital Data Storage (DDS) tape format or in Digital 121Data Storage, Data Compressed (DDS-DC) tape format. 122Since it is a 123variable-length tape device, the number of bytes in a physical record may vary. 124The recording formats available are standard 2Gbyte and compressed format. 125.Ss "Persistent Error Handling" 126Persistent error handling is a modification of the current error handling 127behaviors, BSD and SVR4. 128With persistent error handling enabled, all tape 129operations after an error or exception will return immediately with an error. 130Persistent error handling can be most useful with asynchronous tape operations 131that use the 132.Xr aioread 3C 133and 134.Xr aiowrite 3C 135functions. 136.Pp 137To enable persistent error handling, the ioctl 138.Dv MTIOCPERSISTENT 139must be issued. 140If this ioctl succeeds, then persistent error handling is enabled and 141changes the current error behavior. 142This ioctl will fail if the device driver 143does not support persistent error handling. 144.Pp 145With persistent error handling enabled, all tape operations after an exception 146or error will return with the same error as the first command that failed; the 147operations will not be executed. 148An exception is some event that might stop 149normal tape operations, such as an End Of File (EOF) mark or an End Of Tape 150(EOT) mark. 151An example of an error is a media error. 152The 153.Dv MTIOCLRERR 154ioctl must be issued to allow normal tape operations to continue and to clear 155the error. 156.Pp 157Disabling persistent error handling returns the error behavior to normal SVR4 158error handling, and will not occur until all outstanding operations are 159completed. 160Applications should wait for all outstanding operations to complete 161before disabling persistent error handling. 162Closing the device will also 163disable persistent error handling and clear any errors or exceptions. 164.Pp 165The 166.Sx Read Operation 167and 168.Sx Write Operation 169subsections contain more pertinent information regarding persistent error handling. 170.Ss "Read Operation" 171The 172.Xr read 2 173function reads the next record on the tape. 174The record size is passed back as the number of bytes read, provided it is not 175greater than the number requested. 176When a tape mark or end of data is read, a zero byte count is 177returned; all successive reads after the zero read will return an error and 178.Va errno 179will be set to 180.Er EIO . 181To move to the next file, an 182.Dv MTFSF 183ioctl can be issued before or after the read causing the error. 184This error 185handling behavior is different from the older 186.Sy BSD 187behavior, where another read will fetch the first record of the next tape file. 188If the 189.Sy BSD 190behavior is required, device names containing the letter 191.Ql b 192(for 193.Sy BSD 194behavior) in the final component should be used. 195If persistent error handling 196was enabled with either the BSD or SVR4 tape device behavior, all operations 197after this read error will return 198.Er EIO 199errors until the 200.Dv MTIOCLRERR 201ioctl is issued. 202An 203.Dv MTFSF 204ioctl can then be issued. 205.Pp 206Two successful successive reads that both return zero byte counts indicate 207.Sy EOM 208on the tape. 209No further reading should be performed past the 210.Sy EOM . 211.Pp 212Fixed-length I/O tape devices require the number of bytes read to be a multiple 213of the physical record size. 214For example, 1/4\(dq cartridge tape devices only read 215multiples of 512 bytes. 216If the blocking factor is greater than 64,512 bytes 217(minphys limit), fixed-length I/O tape devices read multiple records. 218.Pp 219Most tape devices which support variable-length I/O operations may read a range 220of 1 to 65,535 bytes. 221If the record size exceeds 65,535 bytes, the driver reads 222multiple records to satisfy the request. 223These multiple records are limited to 22465,534 bytes. 225Newer variable-length tape drivers may relax the above limitation 226and allow applications to read record sizes larger than 65,534. 227Refer to the 228specific tape driver man page for details. 229.Pp 230Reading past logical 231.Sy EOT 232is transparent to the user. 233A read operation 234should never hit physical EOT. 235.Pp 236Read requests that are lesser than a physical tape record are not allowed. 237Appropriate error is returned. 238.Ss "Write Operation" 239The 240.Xr write 2 241function writes the next record on the tape. 242The record has 243the same length as the given buffer. 244.Pp 245Writing is allowed on 1/4" tape at either the beginning of tape or after the 246last written file on the tape. 247With the Exabyte 8200, data may be appended only 248at the beginning of tape, before a filemark, or after the last written file on 249the tape. 250.Pp 251Writing is not so restricted on 1/2\(dq, 4mm, and the other 8mm cartridge tape 252drives. 253Care should be used when appending files onto 1/2\(dq reel tape devices, 254since an extra file mark is appended after the last file to mark the 255.Sy EOM . 256This extra file mark must be overwritten to prevent the creation of a null file. 257To facilitate write append operations, a space to the 258.Sy EOM 259ioctl is provided. 260Care should be taken when overwriting records; the erase head is just 261forward of the write head and any following records will also be erased. 262.Pp 263Fixed-length I/O tape devices require the number of bytes written to be a 264multiple of the physical record size. 265For example, 1/4\(dq cartridge tape devices 266only write multiples of 512 bytes. 267.Pp 268Fixed-length I/O tape devices write multiple records if the blocking factor is 269greater than 64,512 bytes (minphys limit). 270These multiple writes are limited to 27164,512 bytes. 272For example, if a write request is issued for 65,536 bytes using 273a 1/4\(dq cartridge tape, two writes are issued; the first for 64,512 bytes and 274the second for 1024 bytes. 275.Pp 276Most tape devices which support variable-length I/O operations may write a 277range of 1 to 65,535 bytes. 278If the record size exceeds 65,535 bytes, the driver 279writes multiple records to satisfy the request. 280These multiple records are 281limited to 65,534 bytes. 282As an example, if a write request for 65,540 bytes is 283issued, two records are written; one for 65,534 bytes followed by another 284record for 6 bytes. 285Newer variable-length tape drivers may relax the above 286limitation and allow applications to write record sizes larger than 65,534. 287Refer to the specific tape driver man page for details. 288.Pp 289When logical 290.Sy EOT 291is encountered during a write, that write operation 292completes and the number of bytes successfully transferred is returned (note 293that a 'short write' may have occurred and not all the requested bytes would 294have been transferred. 295The actual amount of data written will depend on the 296type of device being used). 297The next write will return a zero byte count. 298A third write will successfully transfer some bytes (as indicated by the 299returned byte count, which again could be a short write); the fourth will 300transfer zero bytes, and so on, until the physical 301.Sy EOT 302is reached and all writes will 303fail with 304.Er EIO . 305.Pp 306When logical 307.Sy EOT 308is encountered with persistent error handling enabled, 309the current write may complete or be a short write. 310The next write will return a zero byte count. 311At this point an application should act appropriately for 312end of tape cleanup or issue yet another write, which will return the error 313.Er ENOSPC . 314After clearing the exception with 315.Dv MTIOCLRERR , 316the next write will succeed (possibly short), followed by another zero byte 317write count, and then another 318.Er ENOSPC 319error. 320.Pp 321Allowing writes after 322.Sy EOT 323has been encountered enables the flushing of buffers. 324However, it is strongly recommended to terminate the writing and close 325the file as soon as possible. 326.Pp 327Seeks are ignored in tape I/O. 328.Ss "Close Operation" 329Magnetic tapes are rewound when closed, except when the "no-rewind" devices 330have been specified. 331The names of no-rewind device files use the letter 332.Ql n 333as the end of the final component. 334The no-rewind version of 335.Pa /dev/rmt/0l 336is 337.Pa /dev/rmt/0ln . 338In case of error for a no-rewind device, the next open rewinds the device. 339.Pp 340If the driver was opened for reading and a no-rewind device has been specified, 341the close advances the tape past the next filemark (unless the current file 342position is at 343.Sy EOM ) , 344leaving the tape correctly positioned to read the first record of the next file. 345However, if the tape is at the first record of a 346file it doesn't advance again to the first record of the next file. 347These semantics are different from the older 348.Sy BSD 349behavior. 350If 351.Sy BSD 352behavior is required where no implicit space operation is executed on close, 353the non-rewind device name containing the letter 354.Ql b 355(for 356.Sy BSD 357behavior) in the final component should be specified. 358.Pp 359If data was written, a file mark is automatically written by the driver upon 360close. 361If the rewinding device was specified, the tape will be rewound after 362the file mark is written. 363If the user wrote a file mark prior to closing, then 364no file mark is written upon close. 365If a file positioning ioctl, like rewind, 366is issued after writing, a file mark is written before repositioning the tape. 367.Pp 368All buffers are flushed on closing a tape device. 369Hence, it is strongly recommended that the application wait for all buffers to 370be flushed before closing the device. 371This can be done by writing a filemark via 372.Dv MTWEOF , 373even with a zero count. 374.Pp 375Note that for 1/2\(dq reel tape devices, two file marks are written to mark the 376.Sy EOM 377before rewinding or performing a file positioning ioctl. 378If the user 379wrote a file mark before closing a 1/2\(dq reel tape device, the driver will 380always write a file mark before closing to insure that the end of recorded 381media is marked properly. 382If the non-rewinding device was specified, two file 383marks are written and the tape is left positioned between the two so that the 384second one is overwritten on a subsequent 385.Xr open 2 386and 387.Xr write 2 . 388.Pp 389If no data was written and the driver was opened for 390.Sy WRITE-ONLY 391access, one or two file marks are written, thus creating a null file. 392.Pp 393After closing the device, persistent error handling will be disabled and any 394error or exception will be cleared. 395.Sh IOCTLS 396Not all devices support all 397.Sy ioctls . 398The driver returns an 399.Er ENOTTY 400error on unsupported ioctls. 401.Pp 402The following structure definitions for magnetic tape 403.Xr ioctl 2 404commands are from 405.In sys/mtio.h . 406.Pp 407The minor device byte structure is: 408.Bd -literal 40915 7 6 5 4 3 2 1 0 410________________________________________________________________________ 411Unit # BSD Reserved Density Density No rewind Unit # 412Bits 7-15 behavior Select Select on Close Bits 0-1 413.Ed 414.Bd -literal 415/* 416 * Layout of minor device byte: 417 */ 418#define MTUNIT(dev) (((minor(dev) & 0xff80) >> 5) + (minor(dev) & 0x3)) 419#define MT_NOREWIND (1 <<2) 420#define MT_DENSITY_MASK (3 <<3) 421#define MT_DENSITY1 (0 <<3) /* Lowest density/format */ 422#define MT_DENSITY2 (1 <<3) 423#define MT_DENSITY3 (2 <<3) 424#define MT_DENSITY4 (3 <<3) /* Highest density/format */ 425#define MTMINOR(unit) (((unit & 0x7fc) << 5) + (unit & 0x3)) 426#define MT_BSD (1 <<6) /* BSD behavior on close */ 427 428/* Structure for MTIOCTOP - magnetic tape operation command */ 429 430struct mtop { 431 short mt_op; /* operation */ 432 daddr_t mt_count; /* number of operations */ 433}; 434 435/* Structure for MTIOCLTOP - magnetic tape operation command */ 436Works exactly like MTIOCTOP except passes 64 bit mt_count values. 437struct mtlop { 438 short mt_op; 439 short pad[3]; 440 int64_t mt_count; 441}; 442.Ed 443.Pp 444The following operations of 445.Dv MTIOCTOP 446and 447.Dv MTIOCLTOP 448ioctls are supported: 449.Pp 450.Bl -tag -width MTIOCGETERROR -compact -offset 2n 451.It Dv MTWEOF 452Write an end-of-file record 453.It Dv MTFSF 454Forward space over file mark 455.It Dv MTBSF 456Backward space over file mark (1/2", 8mm only) 457.It Dv MTFSR 458Forward space to inter-record gap 459.It Dv MTBSR 460Backward space to inter-record gap 461.It Dv MTREW 462Rewind 463.It Dv MTOFFL 464Rewind and take the drive off-line 465.It Dv MTNOP 466No operation, sets status only 467.It Dv MTRETEN 468Retension the tape (cartridge tape only) 469.It Dv MTERASE 470Erase the entire tape and rewind 471.It Dv MTEOM 472Position to EOM 473.It Dv MTNBSF 474Backward space file to beginning of file 475.It Dv MTSRSZ 476Set record size 477.It Dv MTGRSZ 478Get record size 479.It Dv MTTELL 480Get current position 481.It Dv MTSEEK 482Go to requested position 483.It Dv MTFSSF 484Forward to requested number of sequential file marks 485.It Dv MTBSSF 486Backward to requested number of sequential file marks 487.It Dv MTLOCK 488Prevent media removal 489.It Dv MTUNLOCK 490Allow media removal 491.It Dv MTLOAD 492Load the next tape cartridge into the tape drive 493.It Dv MTIOCGETERROR 494Retrieve error records from the st driver 495.El 496.Bd -literal -offset 2n 497/* structure for MTIOCGET - magnetic tape get status command */ 498 499struct mtget { 500 short mt_type; /* type of magtape device */ 501 502 /* the following two registers are device dependent */ 503 short mt_dsreg; /* "drive status" register */ 504 short mt_erreg; /* "error" register */ 505 506 /* optional error info. */ 507 daddr_t mt_resid; /* residual count */ 508 daddr_t mt_fileno; /* file number of current position */ 509 daddr_t mt_blkno; /* block number of current position */ 510 ushort_t mt_flags; 511 short mt_bf; /* optimum blocking factor */ 512}; 513 514/* structure for MTIOCGETDRIVETYPE - get tape config data command */ 515struct mtdrivetype_request { 516 int size; 517 struct mtdrivetype *mtdtp; 518}; 519struct mtdrivetype { 520 char name[64]; /* Name, for debug */ 521 char vid[25]; /* Vendor id and product id */ 522 char type; /* Drive type for driver */ 523 int bsize; /* Block size */ 524 int options; /* Drive options */ 525 int max_rretries; /* Max read retries */ 526 int max_wretries; /* Max write retries */ 527 uchar_t densities[MT_NDENSITIES]; /* density codes,low->hi */ 528 uchar_t default_density; /* Default density chosen */ 529 uchar_t speeds[MT_NSPEEDS]; /* speed codes, low->hi */ 530 ushort_t non_motion_timeout; /* Seconds for non-motion */ 531 ushort_t io_timeout; /* Seconds for data to from tape */ 532 ushort_t rewind_timeout; /* Seconds to rewind */ 533 ushort_t space_timeout; /* Seconds to space anywhere */ 534 ushort_t load_timeout; /* Seconds to load tape and ready */ 535 ushort_t unload_timeout; /* Seconds to unload */ 536 ushort_t erase_timeout; /* Seconds to do long erase */ 537}; 538.Ed 539.Bd -literal -offset 2n 540/* structure for MTIOCGETPOS and MTIOCRESTPOS - get/set tape position */ 541/* 542 * eof/eot/eom codes. 543 */ 544 typedef enum { 545 ST_NO_EOF, 546 ST_EOF_PENDING, /* filemark pending */ 547 ST_EOF, /* at filemark */ 548 ST_EOT_PENDING, /* logical eot pend. */ 549 ST_EOT, /* at logical eot */ 550 ST_EOM, /* at physical eot */ 551 ST_WRITE_AFTER_EOM /* flag allowing writes after EOM */ 552} pstatus; 553 554typedef enum { invalid, legacy, logical } posmode; 555 556typedef struct tapepos { 557 uint64_t lgclblkno; /* Blks from start of partition */ 558 int32_t fileno; /* Num. of current file */ 559 int32_t blkno; /* Blk number in current file */ 560 int32_t partition; /* Current partition */ 561 pstatus eof; /* eof states */ 562 posmode pmode; /* which pos. data is valid */ 563 char pad[4]; 564} tapepos_t; 565.Ed 566.Pp 567.Bd -ragged -compact 568If the 569.Fa pmode 570is legacy, 571.Fa fileno 572and 573.Fa blkno 574fields are valid. 575.Pp 576If the 577.Fa pmode 578is logical, 579.Fa lgclblkno 580field is valid. 581.Ed 582.Pp 583The 584.Dv MTWEOF 585ioctl is used for writing file marks to tape. 586Not only does 587this signify the end of a file, but also usually has the side effect of 588flushing all buffers in the tape drive to the tape medium. 589A zero count 590.Dv MTWEOF 591will just flush all the buffers and will not write any file marks. 592Because a successful completion of this tape operation will guarantee that all 593tape data has been written to the tape medium, it is recommended that this tape 594operation be issued before closing a tape device. 595.Pp 596When spacing forward over a record (either data or 597.Sy EOF ) , 598the tape head is 599positioned in the tape gap between the record just skipped and the next record. 600When spacing forward over file marks (EOF records), the tape head is positioned 601in the tape gap between the next 602.Sy EOF 603record and the record that follows it. 604.Pp 605When spacing backward over a record (either data or 606.Sy EOF ) , 607the tape head is positioned in the tape gap immediately preceding the tape 608record where the tape head is currently positioned. 609When spacing backward over file marks (EOF records), the tape head is 610positioned in the tape gap preceding the 611.Sy EOF . 612Thus the next read would fetch the 613.Sy EOF . 614.Pp 615Record skipping does not go past a file mark; file skipping does not go past 616the 617.Sy EOM . 618After an 619.Dv MTFSR 620<huge number> command, the driver leaves 621the tape logically positioned 622.Em before 623the 624.Sy EOF . 625A related feature is that 626.Sy EOF Ns s 627remain pending until the tape is closed. 628For example, a program 629which first reads all the records of a file up to and including the \fBEOF\fR 630and then performs an 631.Dv MTFSF 632command will leave the tape positioned just 633after that same 634.Sy EOF , 635rather than skipping the next file. 636.Pp 637The 638.Dv MTNBSF 639and 640.Dv MTFSF 641operations are inverses. 642Thus, an 643.Dq Dv MTFSF \(mi1 644is equivalent to an 645.Dq Dv MTNBSF 1 . 646An 647.Dq Dv MTNBSF 0 648is the same as 649.Dq Dv MTFSF 0 ; 650both position the tape device at the beginning of the current file. 651.Pp 652.Dv MTBSF 653moves the tape backwards by file marks. 654The tape position will end 655on the beginning of the tape side of the desired file mark. 656An 657.Dq Dv MTBSF 0 658will position the tape at the end of the current file, before the filemark. 659.Pp 660.Dv MTBSR 661and 662.Dv MTFSR 663operations perform much like space file operations, 664except that they move by records instead of files. 665Variable-length I/O devices 666(1/2\(dq reel, for example) space actual records; fixed-length I/O devices space 667physical records (blocks). 6681/4\(dq cartridge tape, for example, spaces 512 byte 669physical records. 670The status ioctl residual count contains the number of files 671or records not skipped. 672.Pp 673.Dv MTFSSF 674and 675.Dv MTBSSF 676space forward or backward, respectively, to the next 677occurrence of the requested number of file marks, one following another. 678If there are more sequential file marks on tape than were requested, it spaces 679over the requested number and positions after the requested file mark. 680Note that not all drives support this command and if a request is sent to a 681drive that does not, 682.Er ENOTTY 683is returned. 684.Pp 685.Dv MTOFFL 686rewinds and, if appropriate, takes the device off-line by unloading the tape. 687It is recommended that the device be closed after offlining 688and then re-opened after a tape has been inserted to facilitate portability to 689other platforms and other operating systems. 690Attempting to re-open the device 691with no tape will result in an error unless the 692.Dv O_NDELAY 693flag is used. 694.Po 695See 696.Xr open 2 . 697.Pc 698.Pp 699The 700.Dv MTRETEN 701retension ioctl applies only to 1/4\(dq cartridge tape devices. 702It is used to restore tape tension, improving the tape's soft error rate after 703extensive start-stop operations or long-term storage. 704.Pp 705.Dv MTERASE 706rewinds the tape, erases it completely, and returns to the 707beginning of tape. 708Erasing may take a long time depending on the device and/or 709tapes. 710For time details, refer to the drive specific manual. 711.Pp 712.Dv MTEOM 713positions the tape at a location just after the last file written 714on the tape. 715For 1/4\(dq cartridge and 8mm tape, this is after the last file mark 716on the tape. 717For 1/2\(dq reel tape, this is just after the first file mark but 718before the second (and last) file mark on the tape. 719Additional files can then 720be appended onto the tape from that point. 721.Pp 722Note the difference between 723.Dv MTBSF 724(backspace over file mark) and 725.Dv MTNBSF 726(backspace file to beginning of file). 727The former moves the tape 728backward until it crosses an 729.Sy EOF 730mark, leaving the tape positioned 731.Em before 732the file mark. 733The latter leaves the tape positioned 734.Em after 735the file mark. 736Hence, 737.Dq Dv MTNBSF n 738is equivalent to 739.Dq Dv MTBSF (n+1) 740followed by 741.Dq Dv MTFSF 1 . 742The 1/4\(dq cartridge tape devices do not support 743.Dv MTBSF . 744.Pp 745.Dv MTSRSZ 746and 747.Dv MTGRSZ 748are used to set and get fixed record lengths. 749The 750.Dv MTSRSZ 751ioctl allows variable length and fixed length tape drives that 752support multiple record sizes to set the record length. 753The 754.Fa mt_count 755field of the 756.Vt mtop 757struct is used to pass the record size to/from the 758.Xr st 4D 759driver. 760A value of 761.Ql 0 762indicates variable record size. 763The 764.Dv MTSRSZ 765ioctl makes a variable-length tape device behave like a 766fixed-length tape device. 767Refer to the specific tape driver man page for 768details. 769.Pp 770.Dv MTLOAD 771loads the next tape cartridge into the tape drive. 772This is generally only used with stacker and tower type tape drives which handle 773multiple tapes per tape drive. 774A tape device without a tape inserted can be 775opened with the 776.Dv O_NDELAY 777flag, in order to execute this operation. 778.Pp 779.Dv MTIOCGETERROR 780allows user-level applications to retrieve error records 781from the 782.Xr st 4D 783driver. 784An error record consists of the SCSI command cdb 785which causes the error and a 786.Xr scsi_arq_status 9S 787structure if available. 788The user-level application is responsible for allocating and releasing the 789memory for 790.Fa mtee_cdb_buf 791and 792.Fa scsi_arq_status of each 793.Vt mterror_entry . 794Before issuing the ioctl, the 795.Fa mtee_arq_status_len 796value should be at least equal to 797.Ql sizeof (struct scsi_arq_status) . 798If more sense data than the size of 799.Xr scsi_arq_status 9S 800is desired, the 801.Fa mtee_arq_status_len 802may be larger than 803.Ql sizeof (struct scsi_arq_status) 804by the amount of additional extended sense data desired. 805The 806.Fa es_add_len 807field of 808.Xr scsi_extended_sense 9S 809can be used to determine the amount of valid sense data returned by the device. 810.Pp 811The 812.Dv MTIOCGET 813get status 814.Xr ioctl 2 815call returns the drive ID 816.Pq Fa mt_type , 817sense key error 818.Pq Fa mt_erreg , 819file number 820.Pq Fa mt_fileno , 821optimum blocking factor 822.Pq Fa mt_bf 823and record number 824.Pq Fa mt_blkno 825of the last error. 826The residual count 827.Pq Fa mt_resid 828is set to the number of bytes not transferred or files/records not spaced. 829The flags word 830.Pq Fa mt_flags 831contains information indicating if the device is SCSI, if the device is a reel 832device and whether the device supports absolute file positioning. 833The 834.Fa mt_flags 835also indicates if the device is requesting cleaning media be used, whether the 836device is capable of reporting the requirement of cleaning media and if the 837currently loaded media is WORM (Write Once Read Many) media. 838.Pp 839Note \(em When tape alert cleaning is managed by the st driver, the tape 840target driver may continue to return a 841.Dq drive needs cleaning 842status unless an 843.Dv MTIOCGET 844.Xr ioctl 2 845call is made while the cleaning media is in the drive. 846.Pp 847The 848.Dv MTIOCGETDRIVETYPE 849get drivetype ioctl call returns the name of the 850tape drive as defined in 851.Pa st.conf 852.Pq Fa name , 853Vendor 854.Sy ID 855and model 856.Pq Fa product , 857.Sy ID 858.Pq Fa vid , 859type of tape device 860.Pq Fa type , 861block size 862.Pq Fa size , 863drive options 864.Pq Fa options , 865maximum read retry count 866.Pq Fa max_rretries , 867maximum write retry count 868.Pq Fa max_wretries , 869densities supported by the drive 870.Pq Fa densities , 871and default density of the tape drive 872.Pq Fa default_density . 873.Pp 874The 875.Dv MTIOCGETPOS 876ioctl returns the current tape position of the drive. 877It is returned in struct tapepos as defined in 878.Pa /usr/include/sys/scsi/targets/stdef.h . 879.Pp 880The 881.Dv MTIOCRESTPOS 882ioctl restores a saved position from the 883.Dv MTIOCGETPOS . 884.Ss "Persistent Error Handling IOCTLs and Asynchronous Tape Operations" 885.Bl -tag -width MTIOCPERSISTENTSTATUS -compact 886.It Dv MTIOCPERSISTENT 887enables/disables persistent error handling 888.It Dv MTIOCPERSISTENTSTATUS 889queries for persistent error handling 890.It Dv MTIOCLRERR 891clears persistent error handling 892.It Dv MTIOCGUARANTEEDORDER 893checks whether driver guarantees order of I/O's 894.El 895.Pp 896The 897.Dv MTIOCPERSISTENT 898ioctl enables or disables persistent error handling. 899It takes as an argument a pointer to an integer that turns it either on or off. 900If the ioctl succeeds, the desired operation was successful. 901It will wait for 902all outstanding I/O's to complete before changing the persistent error handling 903status. 904For example, 905.Bd -literal -offset 2n 906int on = 1; 907ioctl(fd, MTIOCPERSISTENT, &on); 908int off = 0; 909ioctl(fd, MTIOCPERSISTENT, &off); 910.Ed 911.Pp 912The 913.Dv MTIOCPERSISTENTSTATUS 914ioctl enables or disables persistent error 915handling. 916It takes as an argument a pointer to an integer inserted by the 917driver. 918The integer can be either 1 if persistent error handling is 919.Sq on , 920or 0 if persistent error handling is 921.Sq off . 922It will not wait for outstanding I/O's. 923For example, 924.Bd -literal -offset 2n 925int query; 926ioctl(fd, MTIOCPERSISTENTSTATUS, &query); 927.Ed 928.Pp 929The 930.Dv MTIOCLRERR 931ioctl clears persistent error handling and allows tape 932operations to continual normally. 933This ioctl requires no argument and will 934always succeed, even if persistent error handling has not been enabled. 935It will wait for any outstanding I/O's before it clears the error. 936.Pp 937The 938.Dv MTIOCGUARANTEEDORDER 939ioctl is used to determine whether the driver 940guarantees the order of I/O's. 941It takes no argument. 942If the ioctl succeeds, the driver will support guaranteed order. 943If the driver does not support guaranteed order, then it should not be used 944for asynchronous I/O with 945.Xr libaio 3lib . 946It will wait for any outstanding I/O's before it returns. 947For example, 948.Bd -literal -offset 2n 949ioctl(fd, MTIOCGUARANTEEDORDER) 950.Ed 951.Pp 952See the 953.Sx Persistent Error Handling 954subsection above for more information on persistent error handling. 955.Ss "Asynchronous and State Change IOCTLS" 956.Bl -tag -width 1n 957.It Dv MTIOCSTATE 958This ioctl blocks until the state of the drive, inserted or ejected, is 959changed. 960The argument is a pointer to a 961.Vt enum mtio_state , 962whose possible enumerations are listed below. 963The initial value should be either the last reported state of the drive, or 964.Dv MTIO_NONE . 965Upon return, the 966enum pointed to by the argument is updated with the current state of the drive. 967.Bd -literal -offset 2n 968enum mtio_state { 969 MTIO_NONE /* Return tape's current state */ 970 MTIO_EJECTED /* Tape state is "ejected" */ 971 MTIO_INSERTED /* Tape state is "inserted" */ 972}; 973.Ed 974.El 975.Pp 976When using asynchronous operations, most ioctls will wait for all outstanding 977commands to complete before they are executed. 978.Ss "IOCTLS for Multi-initiator Configurations" 979.Bl -tag -width MTIOCFORCERESERVE -compact 980.It Dv MTIOCRESERVE 981reserve the tape drive 982.It Dv MTIOCRELEASE 983revert back to the default behavior of reserve on open/release on close 984.It Dv MTIOCFORCERESERVE 985reserve the tape unit by breaking reservation held by another host 986.El 987.Pp 988The 989.Dv MTIOCRESERVE 990ioctl reserves the tape drive such that it does not 991release the tape drive at close. 992This changes the default behavior of releasing the device upon close. 993Reserving the tape drive that is already reserved has no effect. 994For example, 995.Bd -literal -offset 2n 996ioctl(fd, MTIOCRESERVE); 997.Ed 998.Pp 999The 1000.Dv MTIOCRELEASE 1001ioctl reverts back to the default behavior of reserve on 1002open/release on close operation, and a release will occur during the next 1003close. 1004Releasing the tape drive that is already released has no effect. 1005For example, 1006.Bd -literal -offset 2n 1007ioctl(fd, MTIOCRELEASE); 1008.Ed 1009.Pp 1010The 1011.Dv MTIOCFORCERESERVE 1012ioctl breaks a reservation held by another host, interrupting any I/O in 1013progress by that other host, and then reserves the tape unit. 1014This ioctl can be executed only with super-user privileges. 1015It is recommended to open the tape device in 1016.Dv O_NDELAY 1017mode when this ioctl needs to be executed, otherwise the open will fail if 1018another host indeed has it reserved. 1019For example, 1020.Bd -literal -offset 2n 1021ioctl(fd, MTIOCFORCERESERVE); 1022.Ed 1023.Ss "IOCTLS for Handling Tape Configuration Options" 1024.Bl -tag -width MTIOCREADIGNOREEOFS 1025.It Dv MTIOCSHORTFMK 1026enables/disables support for writing short filemarks. 1027This is specific to Exabyte drives. 1028.It Dv MTIOCREADIGNOREILI 1029enables/disables suppress incorrect length indicator (SILI) support during reads 1030.It Dv MTIOCREADIGNOREEOFS 1031enables/disables support for reading past two EOF marks which otherwise indicate 1032End-Of-recording-Media (EOM) in the case of 1/2\(dq reel tape drives 1033.El 1034.Pp 1035The 1036.Dv MTIOCSHORTFMK 1037ioctl enables or disables support for short filemarks. 1038This ioctl is only applicable to Exabyte drives which support short filemarks. 1039As an argument, it takes a pointer to an integer. 1040If 0 (zero) is the specified integer, then long filemarks will be written. 1041If 1 is the specified integer, then short filemarks will be written. 1042The specified tape behavior will be in effect until the device is closed. 1043.Pp 1044For example: 1045.Bd -literal -offset 2n 1046int on = 1; 1047int off = 0; 1048/* enable short filemarks */ 1049ioctl(fd, MTIOSHORTFMK, &on); 1050/* disable short filemarks */ 1051ioctl(fd, MTIOCSHORTFMK, &off); 1052.Ed 1053.Pp 1054Tape drives which do not support short filemarks will return an 1055.Va errno 1056of 1057.Er ENOTTY . 1058.Pp 1059The 1060.Dv MTIOCREADIGNOREILI 1061ioctl enables or disables the suppress incorrect 1062length indicator (SILI) support during reads. 1063As an argument, it takes a pointer to an integer. 1064If 0 (zero) is the specified integer, SILI will not be 1065used during reads and incorrect length indicator will not be suppressed. 1066If 1 is the specified integer, SILI will be used during reads and incorrect 1067length indicator will be suppressed. 1068The specified tape behavior will be in effect until the device is closed. 1069.Pp 1070For example: 1071.Bd -literal -offset 2n 1072int on = 1; 1073int off = 0; 1074ioctl(fd, MTIOREADIGNOREILI, &on); 1075ioctl(fd, MTIOREADIGNOREILI, &off); 1076.Ed 1077.Pp 1078The 1079.Dv MTIOCREADIGNOREEOFS 1080ioctl enables or disables support for reading 1081past double EOF marks which otherwise indicate End-Of-recorded-media (EOM) in 1082the case of 1/2\(dq reel tape drives. 1083As an argument, it takes a pointer to an integer. 1084If 0 (zero) is the specified integer, then double EOF marks indicate 1085End-Of-recorded-media (EOM). 1086If 1 is the specified integer, the double EOF marks no longer indicate EOM, 1087thus allowing applications to read past two EOF marks. 1088In this case it is the responsibility of the application to detect 1089End-Of-recorded-media (EOM). 1090The specified tape behavior will be in effect until the device is closed. 1091.Pp 1092For example: 1093.Bd -literal -offset 2n 1094int on = 1; 1095int off = 0; 1096ioctl(fd, MTIOREADIGNOREEOFS, &on); 1097ioctl(fd, MTIOREADIGNOREEOFS, &off); 1098.Ed 1099.Pp 1100Tape drives other than 1/2\(dq reel tapes will return an 1101.Va errno 1102of 1103.Er ENOTTY . 1104.Sh FILES 1105.Pa /dev/rmt/ Ns Ao unit number Ac \ 1106 Ns Ao density Ac \ 1107 Ns Bo Ao BSD behavior Ac Bc \ 1108 Ns Bo Ao no rewind Ac Bc 1109.Pp 1110Where 1111.Aq density 1112can be 1113.Ql l , 1114.Ql m , 1115.Ql h , 1116.Ql u/c 1117(low, medium, high, ultra/compressed, respectively), the 1118.Aq BSD behavior 1119option is 1120.Ql b , and the 1121.Aq no rewind 1122option is 1123.Ql n . 1124.Pp 1125For example, 1126.Pa /dev/rmt/0hbn 1127specifies unit 0, high density, 1128.Sy BSD 1129behavior and no rewind. 1130.Sh EXAMPLES 1131.Bl -inset 1132.It Sy Example 1 1133Tape Positioning and Tape Drives 1134.Pp 1135Suppose you have written three files to the non-rewinding 1/2\(dq tape device, 1136.Pa /dev/rmt/0ln , 1137and that you want to go back and 1138.Xr dd 8 1139the second file off the tape. 1140The commands to do this are: 1141.Bd -literal -offset 2n 1142mt -F /dev/rmt/0lbn bsf 3 1143mt -F /dev/rmt/0lbn fsf 1 1144dd if=/dev/rmt/0ln 1145.Ed 1146.Pp 1147To accomplish the same tape positioning in a C program, followed by a get 1148status ioctl: 1149.Bd -literal -offset 2n 1150struct mtop mt_command; 1151struct mtget mt_status; 1152mt_command.mt_op = MTBSF; 1153mt_command.mt_count = 3; 1154ioctl(fd, MTIOCTOP, &mt_command); 1155mt_command.mt_op = MTFSF; 1156mt_command.mt_count = 1; 1157ioctl(fd, MTIOCTOP, &mt_command); 1158ioctl(fd, MTIOCGET, (char *)&mt_status); 1159.Ed 1160.Pp 1161or 1162.Bd -literal -offset 2n 1163mt_command.mt_op = MTNBSF; 1164mt_command.mt_count = 2; 1165ioctl(fd, MTIOCTOP, &mt_command); 1166ioctl(fd, MTIOCGET, (char *)&mt_status); 1167.Ed 1168.Pp 1169To get information about the tape drive: 1170.Bd -literal -offset 2n 1171struct mtdrivetype mtdt; 1172struct mtdrivetype_request mtreq; 1173mtreq.size = sizeof(struct mtdrivetype); 1174mtreq.mtdtp = &mtdt; 1175ioctl(fd, MTIOCGETDRIVETYPE, &mtreq); 1176.Ed 1177.El 1178.Sh SEE ALSO 1179.Xr mt 1 , 1180.Xr tar 1 , 1181.Xr open 2 , 1182.Xr read 2 , 1183.Xr write 2 , 1184.Xr aioread 3C , 1185.Xr aiowrite 3C , 1186.Xr ar.h 3HEAD , 1187.Xr st 4D , 1188.Xr dd 8 1189.Pp 1190.%T 1/4 Inch Tape Drive Tutorial 1191