libdevmapper1.02.1-udeb - 2:1.02.175-2.1 main

This is a udeb, or a microdeb, for the debian-installer.
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The Linux Kernel Device Mapper is the LVM (Linux Logical Volume Management)
Team's implementation of a minimalistic kernel-space driver that handles
volume management, while keeping knowledge of the underlying device layout
in user-space. This makes it useful for not only LVM, but software raid,
and other drivers that create "virtual" block devices.