| .TH BLKDISCARD 8 "July 2014" "util-linux" "System Administration" |
| .SH NAME |
| blkdiscard \- discard sectors on a device |
| .SH SYNOPSIS |
| .B blkdiscard |
| [options] |
| .RB [ \-o |
| .IR offset ] |
| .RB [ \-l |
| .IR length ] |
| .I device |
| .SH DESCRIPTION |
| .B blkdiscard |
| is used to discard device sectors. This is useful for solid-state |
| drivers (SSDs) and thinly-provisioned storage. Unlike |
| .BR fstrim (8), |
| this command is used directly on the block device. |
| .PP |
| By default, |
| .B blkdiscard |
| will discard all blocks on the device. Options may be used to modify |
| this behavior based on range or size, as explained below. |
| .PP |
| The |
| .I device |
| argument is the pathname of the block device. |
| .PP |
| .B WARNING: All data in the discarded region on the device will be lost! |
| .SH OPTIONS |
| The |
| .I offset |
| and |
| .I length |
| arguments may be followed by the multiplicative suffixes KiB (=1024), |
| MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is |
| optional, e.g., "K" has the same meaning as "KiB") or the suffixes |
| KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB. |
| .TP |
| .BR \-o , " \-\-offset \fIoffset" |
| Byte offset into the device from which to start discarding. The provided value |
| will be aligned to the device sector size. The default value is zero. |
| .TP |
| .BR \-l , " \-\-length \fIlength" |
| The number of bytes to discard (counting from the starting point). The provided value |
| will be aligned to the device sector size. If the specified value extends past |
| the end of the device, |
| .B blkdiscard |
| will stop at the device size boundary. The default value extends to the end |
| of the device. |
| .TP |
| .BR \-p , " \-\-step \fIlength" |
| The number of bytes to discard within one iteration. The default is to discard |
| all by one ioctl call. |
| .TP |
| .BR \-s , " \-\-secure" |
| Perform a secure discard. A secure discard is the same as a regular discard |
| except that all copies of the discarded blocks that were possibly created by |
| garbage collection must also be erased. This requires support from the device. |
| .TP |
| .BR \-z , " \-\-zeroout" |
| Zero-fill rather than discard. |
| .TP |
| .BR \-v , " \-\-verbose" |
| Display the aligned values of |
| .I offset |
| and |
| .IR length . |
| If the \fB\-\-step\fR option is specified, it prints the discard progress every second. |
| .TP |
| .BR \-V , " \-\-version" |
| Display version information and exit. |
| .TP |
| .BR \-h , " \-\-help" |
| Display help text and exit. |
| .SH AUTHOR |
| .MT lczerner@redhat.com |
| Lukas Czerner |
| .ME |
| .SH SEE ALSO |
| .BR fstrim (8) |
| .SH AVAILABILITY |
| The blkdiscard command is part of the util-linux package and is available |
| .UR https://\:www.kernel.org\:/pub\:/linux\:/utils\:/util-linux/ |
| Linux Kernel Archive |
| .UE . |