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sg_write_long

NAME

sg_write_long - send the SCSI WRITE LONG command

SYNOPSIS

sg_write_long [--16] [--cor_dis] [--help] [--in=IF] [--lba=LBA] [--pblock] [--verbose] [--version] [--wr_uncor] [--xfer_len=BTL] DEVICE

DESCRIPTION

Send the SCSI WRITE LONG (10 or 16 byte) command to DEVICE. The buffer to be written to the DEVICE is filled with 0xff bytes or read from the IF file. This buffer includes the logical data (e.g. 512 bytes) and the ECC bytes.

This utility can be used to generate a MEDIUM ERROR at a specific logical block address. This can be useful for testing error handling. Prior to such a test, the sg_dd utility could be used to copy the original contents of the logical block address to some safe location. After the test the sg_dd utility could be used to write back the original contents of the logical block address. An alternate strategy would be to read the "long" contents of the logical block address with sg_read_long utility prior to testing and restore it with this utility after testing.

Take care: If recoverable errors are being injected (e.g. only one or a few bits changed so that the ECC is able to correct the data) then care should be taken with the settings in the "read write error recovery" mode page. Specifically if the ARRE (for reads) and/or AWRE (for writes) are set then recovered errors will cause the lba to be reassigned (and the old location to be added to the grown defect list (PLIST)). This is not easily reversed and uses the (finite number) of spare sectors set aside for this purpose. If in doubt it is probably safest to clear the ARRE and AWRE bits. These bits can be checked and modified with the sdparm utility. For example: "sdparm -c AWRE,ARRE /dev/sda" will clear the bits until the disk is rebooted.

OPTIONS

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

-S, --16

send a SCSI WRITE LONG (16) command to DEVICE. The default action (in the absence of this option) is to send a SCSI WRITE LONG (10) command.

-c, --cor_dis

sets the correction disabled (i.e 'COR_DIS') bit. This inhibits various other mechanisms such as automatic block reallocation, error recovery and various informational exception conditions being triggered. This bit is new in SBC-3 .

-h, --help

output the usage message then exit.

-i, --in=IF

read data (binary) from file named IF and use it for the SCSI WRITE LONG command. If IF is "-" then stdin is read. If this option is not given then 0xff bytes are used as fill.

-l, --lba=LBA

where LBA is the logical block address of the sector to overwrite. Defaults to lba 0 which is a dangerous block to overwrite on a disk that is in use. Assumed to be in decimal unless prefixed with '0x' or has a traling 'h'. If LBA is larger than can fit in 32 bits then the --16 option should be used.

-p, --pblock

sets the physical block (i.e 'PBLOCK') bit. This instructs DEVICE to use the given data (unless --wr_uncor is also given) to write to the physical block specified by LBA. The default action is to write to the logical block corresponding to the given lba. This bit is new in SBC-3 .

-v, --verbose

increase the degree of verbosity (debug messages).

-V, --version

output version string then exit.

-w, --wr_uncor

sets the "write uncorrected" (i.e 'WR_UNCOR') bit. This instructs the DEVICE to flag the given lba (or the physical block that contains it if --pblock is also given) as having an unrecoverable error associated with it. Note: no data is transferred to DEVICE, other than the command (i.e. the cdb). The default action is to use the provided data (--xfer_len=BTL in length) and write it to DEVICE. This bit is new in SBC-3 .

-x, --xfer_len=BTL

where BTL is the byte transfer length (default to 520). If the given value (or the default) does not match the "long" block size of the device, nothing is written to DEVICE and the appropriate xfer_len value may be deduced from the error response which is printed (to stderr).

NOTES

The LBA and BTL (transfer length) arguments may be followed by the following multiplicative suffixes: c C *1; w W *2; b B *512; k K KiB *1,024; KB *1,000; m M MiB *1,048,576; MB *1,000,000; g G GiB *1,073,741,824; and GB *1,000,000,000 . Also a suffix of the form "x<n>" multiplies the leading number by <n>.

Alternatively numerical values can be given in hexadecimal preceded by either "0x" or "0X" (or with a trailing "h" or "H"). When hex numbers are given, multipliers cannot be used.

To read from a defective sector (that, for example, has been filled with 0xff bytes by this utility) use:

  sg_dd if=DEVICE skip=LBA of=/dev/null bs=512 count=1

To overwrite to a defective sector use:

  sg_dd of=DEVICE seek=LBA if=/dev/zero bs=512 count=1    

This will result in a sector (block) with 512 bytes of 0x0 without a MEDIUM ERROR since the ECC and associated data will be well formed.

The 10 byte SCSI WRITE LONG command limits the logical block address to a 32 bit quantity. For larger lbas use the --16 option for the SCSI WRITE LONG (16) command.

EXIT STATUS

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

AUTHORS

Written by Saeed Bishara. Further work by Douglas Gilbert.

REPORTING BUGS

Report bugs to <dgilbert at interlog dot com>.

COPYRIGHT

Copyright © 2004-2007 Douglas Gilbert
This software is distributed under the GPL version 2. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

sg_read_long, sg_dd (both in sg3_utils), sdparm(sdparm)