1da177e4c3
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
62 lines
1.4 KiB
Plaintext
62 lines
1.4 KiB
Plaintext
dm-linear
|
|
=========
|
|
|
|
Device-Mapper's "linear" target maps a linear range of the Device-Mapper
|
|
device onto a linear range of another device. This is the basic building
|
|
block of logical volume managers.
|
|
|
|
Parameters: <dev path> <offset>
|
|
<dev path>: Full pathname to the underlying block-device, or a
|
|
"major:minor" device-number.
|
|
<offset>: Starting sector within the device.
|
|
|
|
|
|
Example scripts
|
|
===============
|
|
[[
|
|
#!/bin/sh
|
|
# Create an identity mapping for a device
|
|
echo "0 `blockdev --getsize $1` linear $1 0" | dmsetup create identity
|
|
]]
|
|
|
|
|
|
[[
|
|
#!/bin/sh
|
|
# Join 2 devices together
|
|
size1=`blockdev --getsize $1`
|
|
size2=`blockdev --getsize $2`
|
|
echo "0 $size1 linear $1 0
|
|
$size1 $size2 linear $2 0" | dmsetup create joined
|
|
]]
|
|
|
|
|
|
[[
|
|
#!/usr/bin/perl -w
|
|
# Split a device into 4M chunks and then join them together in reverse order.
|
|
|
|
my $name = "reverse";
|
|
my $extent_size = 4 * 1024 * 2;
|
|
my $dev = $ARGV[0];
|
|
my $table = "";
|
|
my $count = 0;
|
|
|
|
if (!defined($dev)) {
|
|
die("Please specify a device.\n");
|
|
}
|
|
|
|
my $dev_size = `blockdev --getsize $dev`;
|
|
my $extents = int($dev_size / $extent_size) -
|
|
(($dev_size % $extent_size) ? 1 : 0);
|
|
|
|
while ($extents > 0) {
|
|
my $this_start = $count * $extent_size;
|
|
$extents--;
|
|
$count++;
|
|
my $this_offset = $extents * $extent_size;
|
|
|
|
$table .= "$this_start $extent_size linear $dev $this_offset\n";
|
|
}
|
|
|
|
`echo \"$table\" | dmsetup create $name`;
|
|
]]
|