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mdconfig (8)
  • >> mdconfig (8) ( FreeBSD man: Команды системного администрирования )

  • BSD mandoc


     - configure and enable memory disks


    -a -t type [-n ] [-o [no option ...] ] [-f file ] [-s size ] [-S sectorsize ] [-u unit ] [-x sectors/track ] [-y heads/cyl ]
    -d -u unit
    -l [-n ] [-v ] [-u unit ]  


    The utility configures and enables md(4) devices.

    Options indicate an action to be performed:

    Attach a memory disk. This will configure and attach a memory disk with the parameters specified and attach it to the system.
    Detach a memory disk from the system and release all resources.
    -t type
    Select the type of the memory disk.

    Storage for this type of memory disk is allocated with malloc(9). This limits the size to the malloc bucket limit in the kernel. If the -o reserve option is not set, creating and filling a large malloc-backed memory disk is a very easy way to panic a system.
    A file specified with -f file becomes the backingstore for this memory disk.
    Storage for this type of memory disk is allocated from buffer memory. Pages get pushed out to the swap when the system is under memory pressure, otherwise they stay in the operating memory. Using swap backing is generally preferable over malloc backing.

    -f file
    Filename to use for the vnode type memory disk. Options -a and -t vnode are implied if not specified.
    List configured devices. If given with -u display details about that particular device. If -v option specified, show all details.
    When printing md device names, print only the unit number without the md prefix.
    -s size
    Size of the memory disk. Size is the number of 512 byte sectors unless suffixed with a b , k , m , g or t which denotes byte, kilobyte, megabyte, gigabyte and terabyte respectively. Options -a and -t swap are implied if not specified.
    -S sectorsize
    Sectorsize to use for malloc backed device.
    -x sectors/track
    See the description of the -y option below.
    -y heads/cylinder
    For malloc or vnode backed devices, the -x and -y options can be used to specify a synthetic geometry. This is useful for constructing bootable images for later download to other devices.
    -o [no option ]
    Set or reset options.

    [no async ]
    For vnode backed devices: avoid IO_SYNC for increased performance but at the risk of deadlocking the entire kernel.
    [no reserve ]
    Allocate and reserve all needed storage from the start, rather than as needed.
    [no cluster ]
    Enable clustering on this disk.
    [no compress ]
    Enable/Disable compression features to reduce memory usage.
    [no force ]
    Disable/Enable extra sanity checks to prevent the user from doing something that might adversely affect the system.
    [no readonly ]
    Enable/Disable readonly mode.

    -u unit
    Request a specific unit number for the md(4) device instead of automatic allocation.



    To create a 4 megabyte malloc(9) backed memory disk. The name of the allocated unit will be output on stdout like ``md3 ''

    mdconfig -a -t malloc -s 4m

    To create a disk named /dev/md4 with /tmp/boot.flp as backing:

    mdconfig -a -t vnode -f /tmp/boot.flp -u 4

    To detach and free all resources used by /dev/md4

    mdconfig -d -u 4

    To create and mount a 128MByte swap backed file system on /tmp

    mdconfig -a -t swap -s 128M -u 10
    newfs -U /dev/md10
    mount /dev/md10 /tmp
    chmod 1777 /tmp

    To create a 5MB file-backed disk ( --a and --t vnode are implied):

    dd if=/dev/zero of=somebackingfile bs=1k count=5k
    mdconfig -f somebackingfile -u 0
    bsdlabel -w md0 auto
    newfs md0c
    mount /dev/md0c /mnt

    To mount an ISO 9660 CD image file:

    mdconfig -a -t vnode -u 10 -f cdimage.iso
    mount_cd9660 /dev/md10 /mnt


    md(4), bsdlabel(8), fdisk(8), mdmfs(8), malloc(9)  


    The utility first appeared in Fx 5.0 as a cleaner replacement for the vn(4) and vnconfig(8) combo.  


    The utility was written by An Poul-Henning Kamp Aq .




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