Provided by: sg3-utils_1.46-3ubuntu2.1_amd64 bug

NAME

       sg_unmap - send SCSI UNMAP command (known as 'trim' in ATA specs)

SYNOPSIS

       sg_unmap   [--all=ST,RN[,LA]]  [--anchor]  [--dry-run]  [--force]  [--grpnum=GN]  [--help]
       [--in=FILE] [--lba=LBA,LBA...] [--num=NUM,NUM...] [--timeout=TO]  [--verbose]  [--version]
       DEVICE

DESCRIPTION

       Send  a SCSI UNMAP command to DEVICE to unmap one or more logical blocks. This command was
       introduced in SBC-3 revision 18 under the broad heading of "logical  block  provisioning".
       Logical  blocks may also be unmapped by the SCSI WRITE SAME command; see the sg_write_same
       utility. The unmap capability is closely related to the ATA DATA  SET  MANAGEMENT  command
       with the "Trim" bit set.

       Logical  blocks  to be unmapped can be specified in one of three ways to this utility. One
       way is by supplying the start LBAs to the '--lba=' option and the corresponding  number(s)
       to  unmap  to the '--num=' option. Another way is by putting start LBA and number to unmap
       pairs in a file whose name is given to the '--in=' option. Alternatively a  large  segment
       or  all  of  a disk (SSD) can be unmapped with the --all=ST_RN[,LA] option. All values are
       assumed to be decimal unless prefixed by "0x" (or "0X") or have a trailing "h" (or "H") in
       which  case  they  are  interpreted  as  hexadecimal.  Suffix multipliers are permitted on
       decimal values (e.g. '--num=1m').

       When the '--lba=' option is given then the '--num=' option must also be given. If one  has
       a  comma  separated  list  as  its  argument  then  the other must have the same number of
       elements in its list. The arguments can use a single space as a separator but need  to  be
       in quotes or escaped to not be misinterpreted by the shell.

       With  the '--in=FILE' option an even number of values must be found and are interpreted as
       pairs: the first value in each pair is a starting LBA and the second value is  the  number
       to  unmap  from  that LBA. Everything from and including a "#" on a line is ignored as are
       blank lines. Values may be comma, space and tab separated or  appear  on  separate  lines.
       Each line should not exceed 1023 bytes in length.

       Since  a  lot  of  data can be lost with this utility, a 15 second "cooling off" period is
       given before any UNMAP commands are sent. During this period the  user  is  reminded  what
       will  happen,  and to which device, so they can use control-C (or some other technique) to
       terminate this utility before any unmapping takes place. This period can be bypassed  with
       the --force option.

OPTIONS

       Arguments to long options are mandatory for short options as well.

       -A, --all=ST,RN[,LA]
              where  ST  is the starting LBA, RN is the repeat number which is the maximum number
              of blocks in each SCSI UNMAP command, and LA, if given, is the last LBA  to  unmap.
              If  LA  is  not given, then the last LBA on the DEVICE is used. That is obtained by
              the SCSI READ CAPACITY command.

       -a, --anchor
              sets the 'Anchor' bit in the command (introduced in sbc3r22).

       -d, --dry-run
              perform all the preparation, including opening DEVICE  plus  sending  a  'standard'
              SCSI  INQUIRY  command (and optionally a READ CAPACITY), but exit before performing
              any SCSI UNMAP commands.

       -f, --force
              bypass the 15 second warning period that occurs before any UNMAP commands are sent.

       -g, --grpnum=GN
              sets the 'Group number' field to GN. Defaults to a value of zero.  GN should  be  a
              value between 0 and 63.

       -h, --help
              output the usage message then exit.

       -I, --in=FILE
              where FILE is a file name containing pairs of values. The first member of each pair
              is a starting LBA and the second member of the pair is the number of logical blocks
              to  unmap  from  and including that starting LBA. Values are interpreted as decimal
              unless indicated otherwise. This option cannot be present with the '--lba=' option.

       -l, --lba=LBA,LBA...
              where LBA,LBA... is a  string  of  comma  (or  space)  separated  values  that  are
              interpreted  as  starting  logical  block  addresses. Each number is interpreted as
              decimal unless prefixed by '0x' or '0X' (or it has  a  trailing  'h'  or  'H').  An
              argument  that  contains  any  space  separators  needs  to be quoted (or otherwise
              escaped). When this option is given then the '--num=' option must also be given and
              they must contain the same number of elements in their arguments.

       -n, --num=NUM,NUM...
              where  NUM,NUM...  is  a  string  of  comma  (or  space)  separated values that are
              interpreted as a number of logical blocks to unmap. Each number is  interpreted  as
              decimal  unless  prefixed  by  '0x' or '0X' (or it has a trailing 'h' or 'H'). Note
              that 0 blocks is acceptable. An argument that contains any space  separators  needs
              to  be  quoted (or otherwise escaped).  When this option is given then the '--lba='
              option must also be given and they must contain the  same  number  of  elements  in
              their arguments.

       -t, --timeout=TO
              where  TO is a timeout value (in seconds) for the UNMAP command.  The default value
              is 60 seconds.

       -v, --verbose
              increase the level of verbosity, (i.e. debug output).

       -V, --version
              print the version string and then exit.

NOTES

       Some limits: an LBA can be up to 64 bits, a NUM up to 32 bits  (imposed  by  structure  of
       UNMAP  SCSI  command  parameter data). The NUM is further constrained by the MAXIMUM UNMAP
       LBA COUNT field in the BLOCK LIMITS VPD page (0xb0). The maximum number of  LBA,NUM  pairs
       is  limited  to  128  by  this utility and may be further constrained by the MAXIMUM UNMAP
       BLOCK DESCRIPTOR COUNT field in the BLOCK LIMITS VPD page.

       Since it is unclear how long the UNMAP command will take to execute a '--timeout="  option
       has  been provided. The default timeout period is 60 seconds. If all the logical blocks on
       a logical unit (e.g.  a disk drive) are to be unmapped then the FORMAT UNIT  SCSI  command
       (see the sg_format utility) may be considered as an alternative.

       Support  for  logical  block provisioning is indicated by the LBPME bit in the response to
       the SCSI READ CAPACITY (16) command (see the sg_readcap utility).

       In SBC-3 revision 25  the  LBPU  and  ANC_SUP  bits  where  added  to  the  Logical  Block
       Provisioning  VPD  page.  When LBPU is set it indicates that the device supports the UNMAP
       command. When the ANC_SUP bit is set it indicates the device supports anchored LBAs.

       The SCSI UNMAP command does the "right thing" with respect to  command  queueing.  However
       its  ATA  counterpart:  the  DATA  SET MANAGEMENT command with the "Trim" bit set does not
       interact well with SATA  queueing  known  as  NCQ.   To  address  this  problem  T13  have
       introduced a new command called SFQ DATA SET MANAGEMENT which also has a Trim bit.

EXAMPLES

       In  the  examples  directory of the sg3_utils package there is a sg_unmap_example.txt file
       that shows the format that the '--in=' option accepts.

       To unmap all blocks from and including LBA 0x2000 to the end of the device (e.g.  disk  or
       SSD) with each SCSI UNMAP command given 1024 blocks to unmap:

         sg_unmap --all=0x2000,1k /dev/sg2

       Add  '--force' to bypass the 15 seconds of warnings. So '--force' is appropriate for batch
       files.

EXIT STATUS

       The exit status of sg_unmap is 0 when it is successful. Otherwise see the sg3_utils(8) man
       page.

AUTHORS

       Written by Douglas Gilbert.

REPORTING BUGS

       Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

       Copyright © 2009-2018 Douglas Gilbert
       This  software  is distributed under a FreeBSD license. There is NO warranty; not even for
       MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

       sg_format,sg_get_lba_status,sg_readcap,sg_vpd,sg_write_same(sg3_utils)