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blkdiscard(8) [centos man page]

BLKDISCARD(8)						       System Administration						     BLKDISCARD(8)

NAME
blkdiscard - discard sectors on a device SYNOPSIS
blkdiscard [-o offset] [-l length] [-s] [-v] device DESCRIPTION
blkdiscard is used to discard device sectors. This is useful for solid-state drivers (SSDs) and thinly-provisioned storage. Unlike fstrim(8) this command is used directly on the block device. By default, blkdiscard will discard all blocks on the device. Options may be used to modify this behavior based on range or size, as explained below. The device argument is the pathname of the block device. WARNING: All data in the discarded region on the device will be lost! OPTIONS
The offset and 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. -h, --help Print help and exit. -o, --offset offset Byte offset in the device from which to discard. Provided value will be aligned to the device sector size. Default value is zero. -l, --length length Number of bytes after starting point to discard. Provided value will be aligned to the device sector size. If the specified value extends past the end of the device, blkdiscard will stop at the device size boundary. Default value extends to the end of the device. -s, --secure Perform secure discard. Secure discard is the same as regular discard except all copies of the discarded blocks possibly created by garbage collection must also be erased. It has to be supported by the device. -v, --verbose Print aligned offset and length arguments. AUTHOR
Lukas Czerner <lczerner@redhat.com> SEE ALSO
fstrim(8) AVAILABILITY
The blkdiscard command is part of the util-linux package and is available Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils/util- linux/>. util-linux October 2012 BLKDISCARD(8)

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FALLOCATE(1)							   User Commands						      FALLOCATE(1)

NAME
fallocate - preallocate space to a file SYNOPSIS
fallocate [-n] [-p] [-o offset] -l length filename DESCRIPTION
fallocate is used to preallocate blocks to a file. For filesystems which support the fallocate system call, this is done quickly by allo- cating blocks and marking them as uninitialized, requiring no IO to the data blocks. This is much faster than creating a file by filling it with zeros. As of the Linux Kernel v2.6.31, the fallocate system call is supported by the btrfs, ext4, ocfs2, and xfs filesystems. The exit code returned by fallocate is 0 on success and 1 on failure. OPTIONS
The length and offset 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. -n, --keep-size Do not modify the apparent length of the file. This may effectively allocate blocks past EOF, which can be removed with a truncate. -p, --punch-hole Punch holes in the file, the range should not exceed the length of the file. -o, --offset offset Specifies the beginning offset of the allocation, in bytes. -l, --length length Specifies the length of the allocation, in bytes. -h, --help Print help and exit. -V, --version Print version and exit. AUTHORS
Eric Sandeen <sandeen@redhat.com> Karel Zak <kzak@redhat.com> SEE ALSO
fallocate(2), posix_fallocate(3), truncate(1) AVAILABILITY
The fallocate command is part of the util-linux package and is available from Linux Kernel Archive <ftp://ftp.kernel.org/pub/linux/utils /util-linux/>. util-linux September 2011 FALLOCATE(1)

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