hdid - HDI driver backing store service

SYNOPSYS

       hdid [ options ] imagefile

DESCRIPTION

       hdid  is  the user-level process which handles the loading
       and decompression of disk image  data  for  the  HDI  disk
       image driver in the Mac OS X kernel.

       hdid  supports  a variety of flat-file and dual-fork image
       formats, including read/write,  read-only,  and  read-only
       compressed formats (which it decompresses on the fly).  It
       automatically decodes AppleSingle and MacBinary file  for-
       mats  and is capable of mounting most images directly from
       http:// URLs.

       hdid is not intended to be run directly.  It  is  intended
       to be invoked by Disk Copy.app or hdiutil(1).

       Please  see  the  section  below  on setting up HTTP image
       servers if you plan to regularly  mount  images  from  web
       servers  or  are  wondering  why  a particular image isn't
       mounting.

OPTIONS

       <imagefile>
              required argument indicating what image to mount

       -help  show available options

       -verbose
              verbose output when inserting an image file

       -debug diagnostic output when inserting an image file

       -quiet When finished inserting the image file, don't  echo
              the dev entry created.

       -trace Trace  I/O being accessed via the hdid process when
              requested by the operating system.  Not recommended
              for general use.

       -readonly
              Insert  the image file read only.  Has no effect on
              read-only (or compressed) images.

       -readwrite
              Insert the image file read/write.  Has no effect on
              read-only  (or  compressed)  images.   Used in some
              cases where a read/write image file  might  default
              to  being inserting read-only (currently not imple-
              Suppress automatic  mounting  of  image/partitions.
              This will result in /dev entries being created, and
              a hdid process in  the  background,  but  will  not
              mount the volumes.

       -shadow [ <shadowfile> ]
              Use/create  a  shadow  file  to avoid modifying the
              image file.  When blocks are being written  to  the
              image  file,  the  writes will be redirected to the
              shadow file, and subsequent reads from  those  sec-
              tors  will  be  retrieved from the shadow file.  If
              not specified, -shadow defaults to image.shadow.

EXAMPLES

              $ hdid funstuff.img

       Present funstuff.img to the filesystems for mounting.

              $ hdid master.img -shadow

       Present master.img to the filesystems for potential mount-
       ing,  redirecting  all write operations to the shadow file
       master.img.shadow.

              $ hdid master.img -shadow /tmp/mastershadowfile

       Present master.img to the filesystems for potential mount-
       ing,  redirecting  all write operations to the shadow file
       mastershadowfile in /tmp.  The shadow file can be  on  any
       mounted read/write filesystem -- use of remote filesystems
       (NFS, AFP) for shadow files is discouraged.

Mounting Images via HTTP

       In addition to mounting image files from local  or  remote
       mounted  filesystems,  one can also mount image files from
       HTTP servers.  For  flat  image  files  (UDIF  images,  or
       AppleSingle/MacBinary encoded NDIF image files) mounting a
       image is a matter of passing the http:// URL to hdid:

              hdid http://server.company.com/Images/master.img

       If the image file to be served via HTTP  is  a  dual  fork
       NDIF  image  that  is  not encoded into a flat-file format
       such as AppleSingle, and the HTTP server is running on Mac
       OS  X,  dual  fork  files on both HFS+ and UFS volumes are
       properly detected and  supported.   Such  dual-fork  files
       must  be  moved  or  copied using the Finder or with ditto
       -rsrcFork.  Properly copied NDIF image files on a UFS vol-
       ume  would have a ._filename file in addition to the file-
       name you see in the Finder (i.e.   master.img  would  also
       have ._master.img in the same directory).

       the second fork of a file.

       Accessing  dual fork files on HFS+ filesystems via HTTP is
       only supported if the HTTP server is on a Mac OS X system.
       It  is  possible that some options on the web server could
       disable access to the resource fork on an HFS+ volume, but
       no such options have yet been found.

       were  properly created as AppleDouble files containing the
       resource forks of the UDIF image files).

       Browsing images via HTTP is  much  more  pleasant  if  the
       server  settings  are  modified  to  be  more  friendly to
       highly-persistent clients.  In particular for apache, Max-
       KeepAliveRequests should be increased significantly beyond
       100 or set to 0 (unlimited) and KeepAliveTimeout should be
       boosted to at least 30.  Increasing the number of simulta-
       neous  clients  may  also  be  desirable  because  of  the
       increased  delay before clients are forcibly disconnected.

FILES

       /usr/libexec/load_hdi         SUID executable used to load
                                     HDI disk image driver

SEE ALSO

       hdiutil(1) ditto(8)