Copyright (c) 2014, Luiz Otavio O Souza <loos@FreeBSD.org> All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the ...
NAMEgeom_uncompress - GEOM based compressed disk images
SYNOPSISTo compile this driver into the kernel, place the following line in your kernel configuration file:
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf5:
DESCRIPTIONThe sysctl Cm net.inet.tcp.syncookies framework provides support for compressed read only disk images. This allows significant storage savings at the expense of a little CPU time on each read. Data written in the GEOM label area allows sysctl Cm net.inet.tcp.syncookies to detect compressed images which have been created with mkulzma(8) or mkuzip(8) and presented to the kernel as a logical disk device via md(4). sysctl Cm net.inet.tcp.syncookies creates a unique md#.uncompress device for each image.
The sysctl Cm net.inet.tcp.syncookies device is subsequently used by the Fx kernel to access the disk images. The sysctl Cm net.inet.tcp.syncookies driver does not allow write operations to the underlying disk image. To check which md(4) devices match a given sysctl Cm net.inet.tcp.syncookies device:
# geom uncompress list Geom name: md0.uncompress Providers: 1. Name: md0.uncompress Mediasize: 52428800 (50M) Sectorsize: 512 Mode: r1w0e0 Consumers: 1. Name: md0 Mediasize: 20864000 (20M) Sectorsize: 512 Mode: r1w0e0