hdiutil(1) BSD General Commands Manual hdiutil(1)
NAME
hdiutil -- manipulate disk images (attach, verify, burn, etc)
SYNOPSIS
hdiutil verb [options]
DESCRIPTION
hdiutil uses the DiskImages framework to manipulate disk images. Common
verbs include attach, detach, verify, create, convert, compact, and burn.
The rest of the verbs are currently: help, info, checksum, chpass,
erasekeys, unflatten, flatten, imageinfo, isencrypted, mountvol, unmount,
plugins, udifrez, udifderez, internet-enable, resize, segment,
makehybrid, and pmap.
BACKGROUND
Disk images are data containers that emulate disks. Like disks, they can
be partitioned and formatted. Many common uses of disk images blur the
distinction between the disk image container and its content, but this
distinction is critical to understanding how disk images work. The terms
"attach" and "detach" are used to distinguish the way disk images are
connected to and disconnected from a system. "Mount" and "unmount" are
the parallel filesystems options.
For example, when you double-click a disk image in the Mac OS X Finder,
two separate things happen. First, the image is "attached" to the system
just like an external drive. Then, the kernel and Disk Arbitration probe
the new device for recognized file structures. If any are discovered
that should be mounted, the associated volumes will mount and appear on
the desktop.
When using disk images, always consider whether an operation applies to
the blocks of the disk image container or to the (often file-oriented)
content of the image. For example, hdiutil verify verifies that the
blocks stored in a read-only disk image have not changed since it was
created. It does not check whether the filesystem stored within the
image is self-consistent (as diskutil verifyVolume would). On the other
hand, hdiutil create -srcfolder creates a disk image container, puts a
filesystem in it, and then copies the specified files to the new filesys-
tem.
COMMON OPTIONS
The following option descriptions apply to all verbs:
-verbose be verbose: produce extra progress output and error diagnostics.
This option can help the user decipher why a particular opera-
tion failed. At a minimum, the probing of any specified images
will be detailed.
-quiet close stdout and stderr, leaving only hdiutil's exit status to
indicate success or failure. No /dev entries or mount points
will be printed. -debug and -verbose disable -quiet.
-debug be very verbose. This option is good if a large amount of
progress information is needed. As of Mac OS X 10.6, -debug
enables -verbose.
Many hdiutil verbs understand the following options:
-plist provide result output in plist format. Other programs
invoking hdiutil are expected to use -plist rather than
try to parse the human-readable output. The usual output
is consistent but generally unstructured.
-puppetstrings provide progress output that is easy for another program
to parse. PERCENTAGE outputs can include the value -1
which means hdiutil is performing an operation that will
take an indeterminate amount of time to complete. Any
program trying to interpret hdiutil's progress should use
-puppetstrings.
-srcimagekey key=value
specify a key/value pair for the disk image recognition
system. (-imagekey is normally a synonym)
-tgtimagekey key=value
specify a key/value pair for any image created.
(-imagekey is only a synonym if there is no input image).
-encryption [AES-128|AES-256]
specify a particular type of encryption or, if not speci-
fied, the default encryption algorithm. As of 10.7, the
default algorithm is the AES cipher running in CBC mode
on 512-byte blocks with a 128-bit key.
-stdinpass read a null-terminated passphrase from standard input.
If the standard input is a tty, the passphrase will be
read with readpassphrase(3). Otherwise, the password is
read from stdin. -stdinpass replaces -passphrase which
has been deprecated. -passphrase is insecure because its
argument appears in the output of ps(1) where it is visi-
ble to other users and processes on the system. See
EXAMPLES.
-agentpass force the default behavior of prompting for a passphrase.
Useful with -pubkey to create an image protected by both
a passphrase and a public key.
-recover keychain_file
specify a keychain containing the secret corresponding to
the certificate specified with -certificate when the
image was created.
-certificate cert_file
specify a secondary access certificate for an encrypted
image. cert_file must be DER-encoded certificate data,
which can be created by Keychain Access or openssl(1).
-pubkey PK1,PK2,...,PKn
specify a list of public keys, identified by their hexa-
decimal hashes, to be used to protect the encrypted image
being created.
-cacert cert specify a certificate authority certificate. cert can be
either a PEM file or a directory of certificates pro-
cessed by c_rehash(1). See also --capath and --cacert in
curl(1).
-insecurehttp ignore SSL host validation failures. Useful for self-
signed servers for which the appropriate certificates are
unavailable or if access to a server is desired when the
server name doesn't match what is in the certificate.
-shadow [shadowfile]
Use a shadow file in conjunction with the data in the
primary image file. This option prevents modification of
the original image and allows read-only images to be
attached read/write. When blocks are being read from the
image, blocks present in the shadow file override blocks
in the base image. All data written to an attached
device will be redirected to the shadow file. If not
specified, shadowfile defaults to image.shadow. If the
shadow file does not exist, it is created. hdiutil verbs
taking images as input accept -shadow, -cacert, and
-insecurehttp.
Verbs that create images automatically append the correct extension to
any filenames if the extension is not already present. The creation
engine also examines the filename extension of the provided filename and
changes its behavior accordingly. For example, a sparse image can be
created without specifying -type SPARSEBUNDLE simply by appending the
.sparsebundle extension to the provided filename.
VERBS
Each verb is listed with its description and individual arguments. Argu-
ments to the verbs can be passed in any order. A sector is 512 bytes.
help display minimal usage information for each verb. hdiutil verb
-help will provide basic usage information for that verb.
attach image [options]
attach a disk image as a device. attach will return informa-
tion about an already-attached image as if it had attached it.
If any associated volumes are unmounted (and mounting is not
suppressed), they will be remounted. mount is a poorly-named
synonym for attach. See BACKGROUND.
By default, the system applies additional mount options to
filesystems backed by untrusted devices like disk images:
options like nosuid and quarantine. PERMISSIONS VS. OWNERS
explains the behavior of such filesystems and EXAMPLES shows
how to override some of the default behavior.
The output of attach has been stable since OS X 10.0 (though
it was called hdid(8) then) and is intended to be program-
readable. It consists of the /dev node, a tab, a content hint
(if applicable), another tab, and a mount point (if any
filesystems were mounted). Because content hints are derived
from the partition data, GUID Partition Table types may leak
through. Common GUIDs such as "48465300-0000-11AA-
AA11-0030654" are mapped to their human-readable counterparts
(here "Apple_HFS").
Common options: -encryption, -stdinpass, -recover, -imagekey,
-shadow, -puppetstrings, and -plist.
Options:
-readonly force the resulting device to be read-only
-readwrite attempt to override the DiskImages frame-
work's decision to attach a particular
image read-only. For example, -readwrite
can be used to modify the HFS filesystem on
a HFS/ISO hybrid CD image.
-nokernel attach with a helper process. This is
(again) the default as of Mac OS X 10.5.
-kernel attempt to attach this image without a
helper process; fail if unsupported. Only
UDRW, UDRO, UDZO, and UDSP images are sup-
ported in-kernel. Encryption and HTTP are
supported by the kernel driver.
-notremovable prevent this image from being detached.
Only root can use this option. A reboot is
necessary to cleanly detach an image
attached with -notremovable.
-mount required|optional|suppressed
indicate whether filesystems in the image
should be mounted or not. The default is
required (attach will fail if no filesys-
tems mount).
-nomount identical to -mount suppressed.
-mountroot path mount volumes on subdirectories of path
instead of under /Volumes. path must
exist. Full mount point paths must be less
than MNAMELEN characters (increased from 90
to 1024 in OS X 10.6).
-mountrandom path like -mountroot, but mount point directory
names are randomized with mkdtemp(3).
-mountpoint path assuming only one volume, mount it at path
instead of in /Volumes. See fstab(5) for
ways a system administrator can make par-
ticular volumes automatically mount in par-
ticular filesystem locations by editing the
file /etc/fstab.
-nobrowse render any volumes invisible in applica-
tions such as the OS X Finder.
-owners on|off specify that owners on any filesystems be
honored or not.
-drivekey key=value
specify a key/value pair to be set on the
device in the IOKit registry.
-section subspec
Attach a subsection of a disk image.
subspec is any of <offset>, <first-last>,
or <start,count> in 0-based sectors.
Ranges are inclusive.
The following options have corresponding elements in the
com.apple.frameworks.diskimages preferences domain and thus
can be rendered in both the positive and the negative to over-
ride any existing preferences.
-[no]verify do [not] verify the image. By default,
hdiutil attach attempts to intelligently
verify images that contain checksums before
attaching them. If hdiutil can write to an
image it has verified, attach will store an
attribute with the image so that it will not
be verified again unless its timestamp
changes. To maintain backwards compatibil-
ity, hdid(8) does not attempt to verify
images before attaching them.
Preferences keys: skip-verify, skip-verify-
remote, skip-verify-locked, skip-previously-
verified
-[no]ignorebadchecksums
specify whether bad checksums should be
ignored. The default is to abort when a bad
checksum is detected.
Preferences key: ignore-bad-checksums
-[no]idme do [not] perform IDME actions on IDME
images. IDME actions are not performed by
default.
Preferences key: skip-idme
-[no]idmereveal do [not] reveal (in the Finder) the results
of IDME processing.
Preferences key: skip-idme-reveal
-[no]idmetrash do [not] put IDME images in the trash after
processing.
Preferences key: skip-idme-trash
-[no]autoopen do [not] auto-open volumes (in the Finder)
after attaching an image. By default, dou-
ble-clicking a read-only disk image causes
the resulting volume to be opened in the
Finder. hdiutil defaults to -noautoopen.
-[no]autoopenro do [not] auto-open read-only volumes.
Preferences key: auto-open-ro-root
-[no]autoopenrw do [not] auto-open read/write volumes.
Preferences key: auto-open-rw-root
-[no]autofsck do [not] force automatic file system check-
ing before mounting a disk image. By
default, only quarantined images (e.g. down-
loaded from the Internet) that have not pre-
viously passed fsck are checked.
Preferences key: auto-fsck
detach dev_name [-force]
detach a disk image and terminate any associated process.
dev_name is a partial /dev node path (e.g. "disk1"). As of OS
X 10.4, dev_name can also be a mountpoint. If Disk Arbitra-
tion is running, detach will use it to unmount any filesystems
and detach the image. If not, detach will attempt to unmount
any filesystems and detach the image directly (using the
`eject' ioctl). If Disk Arbitration is not running, it may be
necessary to unmount the filesystems with umount(8) before
detaching the image. eject is a synonym for detach. In com-
mon operation, detach is very similar to diskutil(8)'s eject.
Options:
-force ignore open files on mounted volumes, etc.
verify image [options]
compute the checksum of a "read-only" or "compressed" image
and verify it against the value stored in the image.
Read/write images don't contain checksums and thus can't be
verified. verify accepts the common options -encryption,
-stdinpass, -srcimagekey, -puppetstrings, and -plist.
create size_spec image
create a new image of the given size or from the provided
data. If image already exists, -ov must be specified or
create will fail. To make a cross-platform CD or DVD, use
makehybrid instead. See also EXAMPLES below.
The size specified is the size of the image to be created.
Filesystem and partition layout overhead (80 sectors for the
default GPTSPUD layout on Intel machines) may not be available
for the filesystem and user data in the image.
Size specifiers:
-size ??b|??k|??m|??g|??t|??p|??e
Specify the size of the image in the style of
mkfile(8) with the addition of tera-, peta-, and
exa-bytes sizes (note that 'b' specifies a number
of sectors, not bytes). The larger sizes are use-
ful for large sparse images.
-sectors sector_count
Specify the size of the image file in 512-byte sec-
tors.
-megabytes size
Specify the size of the image file in megabytes
(1024*1024 bytes).
-srcfolder source
copies file-by-file the contents of source into
image, creating a fresh (theoretically defrag-
mented) filesystem on the destination. The result-
ing image is thus recommended for use with asr(8)
since it will have a minimal amount of unused
space. Its size will be that of the source data
plus some padding for filesystem overhead. The
filesystem type of the image volume will match that
of the source as closely as possible unless over-
ridden with -fs. Other size specifiers, such as
-size, will override the default size calculation
based on the source content, allowing for more or
less free space in the resulting filesystem.
-srcfolder can be specified more than once, in
which case the image volume will be populated at
the top level with a copy of each specified
filesystem object. -srcdir is a synonym.
-srcdevice device
specifies that the blocks of device should be used
to create a new image. The image size will match
the size of device. resize can be used to adjust
the size of resizable filesystems and writable
images. Both -srcdevice and -srcfolder can run
into errors if there are bad blocks on a disk. One
way around this problem is to write over the files
in question in the hopes that the drive will remap
the bad blocks. Data will be lost, but the image
creation operation will subsequently succeed.
Filesystem options (like -fs, -volname, -stretch,
or -size) are invalid and ignored when using
-srcdevice.
Common options: -encryption, -stdinpass, -certificate,
-pubkey, -imagekey, -tgtimagekey, -puppetstrings, and -plist.
-imagekey di-sparse-puma-compatible=TRUE and -imagekey
di-shadow-puma-compatible=TRUE will create, respectively,
sparse and shadow images that can be attached on OS X 10.1.
-imagekey encrypted-encoding-version can select between ver-
sion 1 and version 2 of the encrypted encoding. The framework
preferences have a corresponding key to change the default for
all images. Version 2 is not compatible with OS X 10.2 but is
more robust for SPARSE (UDSP) images. Version 1 is the
default for non-sparse images. As of OS X 10.4.7, sparse
encrypted images always use version 2 and as of OS X 10.5, all
encrypted images default to version 2.
General options:
-align alignment
specifies a size to which the final data partition
will be aligned. The default is 4K.
-type UDIF|SPARSE|SPARSEBUNDLE
-type is particular to create and is used to specify
the format of empty read/write images. It is inde-
pendent of -format which is used to specify the
final read-only image format when populating an
image with pre-existing content.
UDIF is the default type. If specified, a UDRW of
the specified size will be created. SPARSE creates
a UDSP: a read/write single-file image which expands
as is is filled with data. SPARSEBUNDLE creates a
UDSB: a read/write image backed by a directory bun-
dle.
By default, UDSP images grow one megabyte at a time.
Introduced in 10.5, UDSB images use 8 MB band files
which grow as they are written to. -imagekey
sparse-band-size=size can be used to specify the
number of 512-byte sectors that will be added each
time the image grows. Valid values for SPARSEBUNDLE
range from 2048 to 16777216 sectors (1 MB to 8 GB).
The maximum size of a SPARSE image is 128 petabytes;
the maximum for SPARSEBUNDLE is just under 8
exabytes (2^63 - 512 bytes minus 1 byte). The
amount of data that can be stored in either type of
sparse image is additionally bounded by the filesys-
tem in the image and by any partition map. compact
can reclaim unused bands in sparse images backing
HFS+ filesystems. resize will only change the vir-
tual size of a sparse image. See also USING PERSIS-
TENT SPARSE IMAGES below.
-fs filesystem
where filesystem is one of HFS+, HFS+J (JHFS+),
HFSX, JHFS+X, MS-DOS, or UDF. -fs causes a filesys-
tem of the specified type to be written to the
image. -fs may change the partition scheme and type
appropriately. -fs will not make any size adjust-
ments: if the image is the wrong size for the speci-
fied filesystem, create will fail. -fs is invalid
and ignored when using -srcdevice.
-volname volname
The newly-created filesystem will be named volname.
The default depends the filesystem being used;
HFS+'s default volume name is `untitled'. -volname
is invalid and ignored when using -srcdevice.
-uid uid the root of the newly-created volume will be owned
by the given numeric user id. 99 maps to the magic
`unknown' user (see hdid(8)).
-gid gid the root of the newly-created volume will be owned
by the given numeric group id. 99 maps to
`unknown'.
-mode mode the root of the newly-created volume will have mode
(in octal) mode. The default mode is determined by
the filesystem's newfs unless -srcfolder is speci-
fied, in which case the default mode is derived from
the specified filesystem object.
-[no]autostretch
do [not] suppress automatically making backwards-
compatible stretchable volumes when the volume size
crosses the auto-stretch-size threshold (default:
256 MB). See also asr(8).
-stretch max_stretch
-stretch initializes HFS+ filesystem data such that
it can later be stretched on older systems (which
could only stretch within predefined limits) using
hdiutil resize or by asr(8). max_stretch is speci-
fied like -size. -stretch is invalid and ignored
when using -srcdevice.
-fsargs newfs_args
additional arguments to pass to whatever newfs pro-
gram is implied by -fs. newfs_hfs(8) has a number
of options that can reduce the amount of space
needed by the filesystem's data structures. Sup-
pressing the journal with -fs HFS+ and passing argu-
ments such as -c c=64,a=16,e=16 to -fsargs will min-
imize gaps at the front of the filesystem, allowing
resize to squeeze more space from the filesystem.
For truly optimal filesystems, use makehybrid.
-layout layout
Specify the partition layout of the image. layout
can be anything supported by MediaKit.framework.
NONE creates an image with no partition map. When
such an image is attached, a single /dev entry will
be created (e.g. /dev/disk1).
`SPUD' causes a DDM and an Apple Partition Scheme
partition map with a single entry to be written.
`GPTSPUD' creates a similar image but with a GUID
Partition Scheme map instead. When attached, multi-
ple /dev entries will be created, with either slice
1 (GPT) or slice 2 (APM) as the data partition.
(e.g. /dev/disk1, /dev/disk1s1, /dev/disk1s2).
Unless overridden by -fs, the default layout is
`GPTSPUD' (PPC systems used `SPUD' prior to OS X
10.6). Other layouts include `MBRSPUD' and `ISOCD'.
create -help lists all supported layouts.
-library bundle
specify an alternate layout library. The default is
MediaKit's MKDrivers.bundle.
-partitionType partition_type
Change the type of partition in a single-partition
disk image. The default is Apple_HFS unless -fs
implies otherwise.
-ov overwrite an existing file. The default is not to
overwrite existing files.
-attach attach the image after creating it. If no filesys-
tem is specified via -fs, the attach will fail per
the default attach -mount required behavior.
Image from source options (for -srcfolder and -srcdevice):
-format format Specify the final image format. The default
when a source is specified is UDZO. format can
be any of the format parameters used by
convert.
Options specific to -srcdevice:
-segmentSize size_spec
Specify that the image should be written in
segments no bigger than size_spec (which fol-
lows -size conventions).
Options specific to -srcfolder:
-[no]crossdev do [not] cross device boundaries on the source
filesystem.
-[no]scrub do [not] skip temporary files when imaging a
volume. Scrubbing is the default when the
source is the root of a mounted volume.
Scrubbed items include trashes, temporary
directories, swap files, etc.
-[no]anyowners do not fail if the user invoking hdiutil can't
ensure correct file ownership for the files in
the image.
-skipunreadable skip files that can't be read by the copying
user and don't authenticate.
-copyuid user perform the copy as the given user. Requires
root privilege. If user can't read or create
files with the needed owners, -anyowners or
-skipunreadable must be used to prevent the
operation from failing.
By default, create -srcfolder attempts to maintain the permis-
sions present in the source directory. It prompts for authen-
tication if it detects an unreadable file, a file owned by
someone other than the user creating the image, or a SGID file
in a group that the copying user is not in.
convert image -format format -o outfile
convert image to type format and write the result to outfile.
As with create, the correct filename extension will be added
only if it isn't part of the provided name. Format is one of:
UDRW - UDIF read/write image
UDRO - UDIF read-only image
UDCO - UDIF ADC-compressed image
UDZO - UDIF zlib-compressed image
UDBZ - UDIF bzip2-compressed image (OS X 10.4+ only)
UFBI - UDIF entire image with MD5 checksum
UDRo - UDIF read-only (obsolete format)
UDCo - UDIF compressed (obsolete format)
UDTO - DVD/CD-R master for export
UDxx - UDIF stub image
UDSP - SPARSE (grows with content)
UDSB - SPARSEBUNDLE (grows with content; bundle-backed)
RdWr - NDIF read/write image (deprecated)
Rdxx - NDIF read-only image (Disk Copy 6.3.3 format)
ROCo - NDIF compressed image (deprecated)
Rken - NDIF compressed (obsolete format)
DC42 - Disk Copy 4.2 image
In addition to the compression offered by some formats, the
UDIF and NDIF read-only formats skip unused space in HFS, UFS,
and MS-DOS (FAT) filesystems. For UDZO, -imagekey
zlib-level=value allows the zlib compression level to be spec-
ified ala gzip(1). The default compression level is 1
(fastest).
Common options: -encryption, -stdinpass, -certificate,
-srcimagekey, -tgtimagekey, -shadow and related,
-puppetstrings, and -plist.
Other options:
-align alignment
The default is 4 (2K).
-pmap add partition map.
When converting a NDIF to a any variety of UDIF,
or when converting an unpartitioned UDIF, the
default is true.
-segmentSize [size_spec]
Specify segmentation into size_spec-sized seg-
ments as outfile is being written. The default
size_spec when -segmentSize is specified alone is
2*1024*1024 (1 GB worth of sectors) for UDTO
images and 4*1024*1024 (2 GB segments) for all
other image types. size_spec can also be speci-
fied ??b|??k|??m|??g|??t??p|??e like create's
-size flag.
-tasks task_count
When converting an image into a compressed for-
mat, specify the number of threads to use for the
compression operation. The default is the number
of processors active in the current system.
burn image
Burn image to optical media in an attached burning device. In
all cases, a prompt for media will be printed once an appro-
priate drive has been found. Common options: -shadow and
related, -srcimagekey, -encryption, -puppetstrings, and
-stdinpass.
Other options:
-device specify a device to use for burning. See
-list.
-testburn don't turn on laser (laser defaults to on).
-anydevice explicitly allow burning to devices not qual-
ified by Apple (kept for backwards compati-
bility as burn will burn to any device by
default as of OS X 10.4).
-[no]eject do [not] eject disc after burning. The
default is to eject the disc.
-[no]verifyburn do [not] verify disc contents after burn.
The default is to verify.
-[no]addpmap do [not] add partition map if necessary.
Some filesystem types will not be recognized
when stored on optical media unless they are
enclosed in a partition map. This option
will add a partition map to any bare filesys-
tem which needs a partition map in order to
be recognized when burned to optical media.
The default is to add the partition map if
needed.
-[no]skipfinalfree do [not] skip final free partition. If
there is a partition map on the image speci-
fying an Apple_Free partition as the last
partition, that Apple_Free partition will not
be burned. The burned partition map will
still reference the empty space. The default
is to skip burning a final free partition.
-[no]optimizeimage do [not] optimize filesystem for burning.
Optimization can reduce the size of an HFS or
HFS+ volume to the size of the data contained
on the volume. This option will change what
is burned such that the disc will have a dif-
ferent checksum than the image it came from.
The default is to burn all blocks of the disk
image (minus any trailing Apple_Free).
-[no]forceclose do [not] force the disc to be closed after
burning. Further burns to the disc will be
impossible. The default is not to close the
disc.
-nounderrun Disable the default buffer underrun protec-
tion.
-[no]synthesize [Don't] Synthesize a hybrid filesystem for
the disc. The default is to create a new
(HFS/ISO) filesystem when the source image's
blocks could not be legally burned to a disc.
-speed x_factor 1, 2, 4, 6, ... `max'
The desired "x-factor". e.g. 8 means the
drive will be instructed burn at "8x speed".
`max' will cause the burn to proceed at the
maximum speed of the drive. `max' is the
default speed. Slower speeds can produce
more reliable burns. The speed factor is
relative to the media being burned (e.g.
-speed 2 has a different data rate when used
for a DVD burn vs. a CD burn). Note that
some drives have a minimum burn speed in
which case any slower speed specified will
result in a burn at the drive's minimum
speed.
-sizequery calculate the size of disc required (the size
returned is in sectors) without burning any-
thing.
-erase prompt for optical media (DVD-RW/CD-RW) and
then, if the hardware supports it, quickly
erase the media. If an image is specified,
it will be burned to the media after the
media has been erased.
-fullerase erase all sectors of the disc (this usually
takes quit a bit longer than -erase).
-list list all burning devices, with OpenFirmware
paths suitable for -device.
makehybrid -o image source
Generate a potentially-hybrid filesystem in a read-only disk
image using the DiscRecording framework's content creation
system. This disk image will represent a data disc.
drutil(1) can be used to make audio discs.
source can either be a directory or a disk image. The gener-
ated image can later be burned using burn, or converted to
another read-only format with convert. By default, the
filesystem will be readable on most modern computing plat-
forms. The generated filesystem is not intended for conver-
sion to read/write, but can safely have its files copied to a
read/write filesystem by ditto(8) or asr(8) (in file-copy
mode).
hdiutil supports generating El Torito-style bootable ISO9660
filesystems, which are commonly used for booting x86-based
hardware. The specification includes several emulation modes.
By default, an El Torito boot image emulates either a 1.2MB,
1.44MB, or 2.88MB floppy drive, depending on the size of the
image. Also available are "No Emulation" and "Hard Disk
Emulation" modes, which allow the boot image to either be
loaded directly into memory, or be virtualized as a parti-
tioned hard disk, respectively. The El Torito options should
not be used for data CDs.
Filesystem options:
-hfs Generate an HFS+ filesystem. This filesystem can be
present on an image simultaneously with an ISO9660 or
Joliet or UDF filesystem. On operating systems that
understand HFS+ as well as ISO9660 and UDF, like Mac
OS 9 or Mac OS X, it is usually the preferred filesys-
tem.
-iso Generate an ISO9660 Level 2 filesystem with Rock Ridge
extensions. This filesystem can be present on an
image simultaneously with an HFS+ or Joliet or UDF
filesystem. ISO9660 is the standard cross-platform
interchange format for CDs and some DVDs, and is
understood by virtually all operating systems. If an
ISO9660 or Joliet filesystem is present on a disk
image or CD, but not HFS+, Mac OS X will use the
ISO9660 (or Joliet) filesystem.
-joliet Generate Joliet extensions to ISO9660. This view of
the filesystem can be present on an image simultane-
ously with HFS+, and requires the presence of an
ISO9660 filesystem. Joliet supports Unicode file-
names, but is only supported on some operating sys-
tems. If both an ISO9660 and Joliet filesystem are
present on a disk image or CD, but not HFS+, Mac OS X
will prefer the Joliet filesystem.
-udf Generate a UDF filesystem. This filesystem can be
present on an image simultaneously with HFS+, ISO9660,
and Joliet. UDF is the standard interchange format for
DVDs, although operating system support varies based
on OS version and UDF version.
By default, if no filesystem is specified, the image will be
created with all four filesystems as a hybrid image. When
multiple filesystems are selected, the data area of the image
is shared between all filesystems, and only directory informa-
tion and volume meta-data are unique to each filesystem. This
means that creating a cross-platform ISO9660/HFS+ hybrid has a
minimal overhead when compared to a single filesystem image.
Other options (most take a single argument):
-hfs-blessed-directory Path to directory which should be
"blessed" for Mac OS X booting on the
generated filesystem. This assumes the
directory has been otherwise prepared,
for example with bless -bootinfo to
create a valid BootX file. (HFS+
only).
-hfs-openfolder Path to a directory that will be opened
by the Finder automatically. See also
the -openfolder option in bless(8)
(HFS+ only).
-hfs-startupfile-size Allocate an empty HFS+ Startup File of
the specified size, in bytes (HFS+
only).
-abstract-file Path to a file in the source directory
(and thus the root of the generated
filesystem) for use as the
ISO9660/Joliet Abstract file
(ISO9660/Joliet).
-bibliography-file Path to a file in the source directory
(and thus the root of the generated
filesystem) for use as the
ISO9660/Joliet Bibliography file
(ISO9660/Joliet).
-copyright-file Path to a file in the source directory
(and thus the root of the generated
filesystem) for use as the
ISO9660/Joliet Copyright file
(ISO9660/Joliet).
-application Application string (ISO9660/Joliet).
-preparer Preparer string (ISO9660/Joliet).
-publisher Publisher string (ISO9660/Joliet).
-system-id System Identification string
(ISO9660/Joliet).
-keep-mac-specific Expose Macintosh-specific files (such
as .DS_Store) in non-HFS+ filesystems
(ISO9660/Joliet).
-eltorito-boot Path to an El Torito boot image within
the source directory. By default,
floppy drive emulation is used, so the
image must be one of 1200KB, 1440KB, or
2880KB. If the image has a different
size, either -no-emul-boot or
-hard-disk-boot must be used to enable
"No Emulation" or "Hard Disk Emulation"
mode, respectively (ISO9660/Joliet).
-hard-disk-boot Use El Torito Hard Disk Emulation mode.
The image must represent a virtual
device with an MBR partition map and a
single partition
-no-emul-boot Use El Torito No Emulation mode. The
system firmware will load the number of
sectors specified by -boot-load-size
and execute it, without emulating any
devices (ISO9660/Joliet).
-no-boot Mark the El Torito image as non-
bootable. The system firmware may still
create a virtual device backed by this
data. This option is not recommended
(ISO9660/Joliet).
-boot-load-seg For a No Emulation boot image, load the
data at the specified segment address.
This options is not recommended, so
that the system firmware can use its
default address (ISO9660/Joliet)
-boot-load-size For a No Emulation boot image, load the
specified number of 512-byte emulated
sectors into memory and execute it. By
default, 4 sectors (2KB) will be loaded
(ISO9660/Joliet).
-eltorito-platform Use the specified numeric platform ID
in the El Torito Boot Catalog Valida-
tion Entry or Section Header. Defaults
to 0 to identify x86 hardware
(ISO/Joliet).
-eltorito-specification For complex layouts involving multiple
boot images, a plist-formatted string
can be provided, using either OpenStep-
style syntax or XML syntax, represent-
ing an array of dictionaries. Any of
the El Torito options can be set in the
sub-dictionaries and will apply to that
boot image only. If
-eltorito-specification is provided in
addition to the normal El Torito com-
mand-line options, the specification
will be used to populate secondary non-
default boot entries.
-udf-version Version of UDF filesystem to generate.
This can be either "1.02" or "1.50".
If not specified, it defaults to "1.50"
(UDF).
-default-volume-name Default volume name for all filesys-
tems, unless overridden. If not speci-
fied, defaults to the last path compo-
nent of source.
-hfs-volume-name Volume name for just the HFS+ filesys-
tem if it should be different (HFS+
only).
-iso-volume-name Volume name for just the ISO9660
filesystem if it should be different
(ISO9660 only).
-joliet-volume-name Volume name for just the Joliet
filesystem if it should be different
(Joliet only).
-udf-volume-name Volume name for just the UDF filesystem
if it should be different (UDF only).
-hide-all A glob expression of files and directo-
ries that should not be exposed in the
generated filesystems. The string may
need to be quoted to avoid shell expan-
sion, and will be passed to glob(3) for
evaluation. Although this option can-
not be used multiple times, an arbi-
trarily complex glob expression can be
used.
-hide-hfs A glob expression of files and directo-
ries that should not be exposed via the
HFS+ filesystem, although the data may
still be present for use by other
filesystems (HFS+ only).
-hide-iso A glob expression of files and directo-
ries that should not be exposed via the
ISO filesystem, although the data may
still be present for use by other
filesystems (ISO9660 only). Per above,
the Joliet hierarchy will supersede the
ISO hierarchy when the hybrid is
mounted as an ISO 9660 filesystem on
Mac OS X. Therefore, if Joliet is
being generated (the default)
-hide-joliet will also be needed to
hide the file from mount_cd9660(8).
-hide-joliet A glob expression of files and directo-
ries that should not be exposed via the
Joliet filesystem, although the data
may still be present for use by other
filesystems (Joliet only). Because OS
X's ISO 9660 filesystem uses the Joliet
catalog if it is available,
-hide-joliet effectively supersedes
-hide-iso when the resulting filesystem
is mounted as ISO on OS X.
-hide-udf A glob expression of files and directo-
ries that should not be exposed via the
UDF filesystem, although the data may
still be present for use by other
filesystems (UDF only).
-only-udf A glob expression of objects that
should only be exposed in UDF.
-only-iso A glob expression of objects that
should only be exposed in ISO.
-only-joliet A glob expression of objects that
should only be exposed in Joliet.
-print-size Preflight the data and calculate an
upper bound on the size of the image.
The actual size of the generated image
is guaranteed to be less than or equal
to this estimate.
-plistin Instead of using command-line parame-
ters, use a standard plist from stan-
dard input to specific the parameters
of the hybrid image generation. Each
command-line option should be a key in
the dictionary, without the leading
"-", and the value should be a string
for path and string arguments, a number
for number arguments, and a boolean for
toggle options. The source argument
should use a key of "source" and the
image should use a key of "output".
If a disk image was specified for source, the image will be
attached and paths will be evaluated relative to the mount-
point of the image. No absolute paths can be used in this
case. If source is a directory, all argument paths should
point to files or directories either via an absolute path, or
via a relative path to the current working directory.
The volume name options, just like files in the filesystems,
may need to be mapped onto the legal character set for a given
filesystem or otherwise changed to obey naming restrictions.
Use drutil(1) as drutil filename myname to see how a given
string would be remapped.
The -abstract-file, -bibliography-file, -and -copyright-file
must exist directly in the source directory, not a sub-direc-
tory, and must have an 8.3 name for compatibility with ISO9660
Level 1.
compact image
scans the bands of a sparse (SPARSE or SPARSEBUNDLE) disk
image containing an HFS filesystem, removing those parts of
the image which are no longer being used by the filesystem.
Depending on the location of files in the hosted filesystem,
compact may or may not shrink the image. For SPARSEBUNDLE
images, completely unused band files are simply removed.
Common options: -encryption, -stdinpass, -srcimagekey, -shadow
and related, -puppetstrings, and -plist.
info display information about DiskImages.framework, the disk image
driver, and any images that are currently attached. hdiutil
info accepts -plist.
checksum image -type type
Calculate the specified checksum on the image data, regardless
of image type.
Common options: -shadow and related, -encryption, -stdinpass,
-srcimagekey, -puppetstrings, and -plist.
type is one of:
UDIF-CRC32 - CRC-32 image checksum
UDIF-MD5 - MD5 image checksum
DC42 - Disk Copy 4.2
CRC28 - CRC-32 (NDIF)
CRC32 - CRC-32
MD5 - MD5
SHA - SHA
SHA1 - SHA-1
SHA256 - SHA-256
SHA384 - SHA-384
SHA512 - SHA-512
chpass image
change the passphrase for an encrypted image. The default is
to change the password interactively.
Common options: -recover and -srcimagekey. The options
-oldstdinpass and -newstdinpass allow, in the order specified,
the null-terminated old and new passwords to be read from the
standard input in the same manner as with -stdinpass.
erasekeys image
securely overwrite keys used to access an encrypted image,
quickly rendering the image completely inaccessible. Once
erasekeys has been run on an encrypted image, there is no fea-
sible way to recover data from the image file.
Common options: -plist and -quiet.
unflatten image
unflatten a UDIF disk image, creating an OS 9-style dual-fork
image file (no XML metadata). If the resource fork represen-
tation of the metadata becomes greater than 16 MB, the opera-
tion will fail with error -39 ("End of fork").
Common options: -encryption, -stdinpass, and -srcimagekey.
flatten image
Flatten a read-only (or compressed) UDIF disk image into a
single-fork file. By default, metadata will be stored both as
XML (for the kernel's use) and in an embedded resource fork
(for OS X 10.1 and earlier).
Common options: -srcimagekey, -encryption, and -stdinpass.
Since images are created "flat" by default, flatten is only
required if the UDIF has previously been unflattened.
Other options:
-noxml don't embed XML data for in-kernel attachment.
The image will never attach in-kernel.
-norsrcfork don't embed resource fork data. The image will
not attach on OS X versions prior to OS X 10.2.
fsid image
Print information about file systems on a given disk image.
Per DEVICE SPECIAL FILES, image can be a /dev entry corre-
sponding to a disk. More detailed information is presented
for HFS file systems.
Common options: -encryption, -stdinpass, -srcimagekey, and
-shadow and related.
mountvol dev_name
mount the filesystem in dev_name using Disk Arbitration (simi-
lar to diskutil(8)'s mount). XML output is available from
-plist. Note that mountvol (rather than mount, though it
often works in OS X 10.5 and later) is the correct way to
remount a volume after it has been unmounted by unmount.
Prior to OS X 10.5, mount/attach would treat a /dev entry as a
disk image to be attached (creating another /dev entry). That
behavior was undesirable.
unmount volume [-force]
unmount a mounted volume without detaching any associated
image. Volume is a /dev entry or mountpoint. NOTE: unmount
does NOT detach any disk image associated with the volume.
Images are attached and detached; volumes are mounted and
unmounted. hdiutil mountvol (or diskutil mount) will remount
a volume that has been unmounted by hdiutil unmount.
Options:
-force unmount filesystem regardless of open files on that
filesystem. Similar to umount -f.
imageinfo image
Print out information about a disk image.
Common options: -encryption, -stdinpass, -srcimagekey, -shadow
and related, and -plist.
Options are any of:
-format just print out the image format
-checksum just print out the image checksum
isencrypted image
print a line indicating whether image is encrypted. If it is,
additional details are printed.
Common options: -plist.
plugins print information about DiskImages framework plugins. The
user, system, local, and network domains are searched for
plugins (i.e. ~/Library/Plug-ins/DiskImages,
/System/Library/Plug-ins/DiskImages,
/Library/Plug-ins/DiskImages,
/Network/Library/Plug-ins/DiskImages).
Common options: -plist.
internet-enable [-yes] | -no | -query image
Enable or disable download post-processing (IDME). -yes is
the default. When enabled, a browser (or Disk Copy 10.2.3+)
will "unpack" the contents: the image's visible contents will
be copied into the directory containing the image and the
image will be put into the trash with IDME disabled.
Common options: -encryption, -stdinpass, -srcimagekey, and
-plist.
resize size_spec image
Resize a disk image or the containers within it. For an image
containing a trailing Apple_HFS partition, the default is to
resize the image container, the partition, and the filesystem
within it by aligning the end of the hosted structures with
the end of the image. hdiutil resize cannot resize filesys-
tems other than HFS+ and its variants.
resize can shrink an image so that its HFS/HFS+ partition can
be converted to CD-R/DVD-R format and still be burned.
hdiutil resize will not reclaim gaps because it does not move
data. diskutil(8)'s resize can move filesystem data which can
help hdiutil resize create a minimally-sized image. -fsargs
can also be used to minimize filesystem gaps inside an image.
resize is limited by the disk image container format (e.g.
UDSP vs. UDSB), any partition scheme, the hosted filesystem,
and the filesystem hosting the image. In the case of HFS+
inside of GPT inside of a UDRW on HFS+ with adequate free
space, the limit is approximately 2^63 bytes. Older images
created with an APM partition scheme are limited by it to 2TB.
Before OS X 10.4, resize was limited by how the filesystem was
created (see hdiutil create -stretch).
hdiutil burn does not burn Apple_Free partitions at the end of
the devices, so an image with a resized filesystem can be
burned to create a CD-R/DVD-R master that contains only the
actual data in the hosted filesystem (assuming minimal data
fragmentation).
Common options: -encryption, -stdinpass, -srcimagekey, -shadow
and related, and -plist.
Size specifiers:
-size ??b|??k|??m|??g|??t??p|??e
-sectors sector_count | min
Specify the number of 512-byte sectors to
which the partition should be resized. If
this falls outside the mininum valid value or
space remaining on the underlying file sys-
tem, an error will be returned and the parti-
tion will not be resized. min automatically
determines the smallest possible size.
Other options:
-imageonly only resize the image file, not the parti-
tion(s) and filesystems inside of it.
-partitiononly only resize a partition / filesystem in the
image, not the image. -partitiononly will
fail if the new size won't fit inside the
image. On APM, shrinking a partition results
in an explicit Apple_Free entry taking up the
remaining space in the image.
-partitionNumber partitionNumber
specifies which partition to resize (UDIF
only -- see HISTORY below). partitionNumber
is 0-based, but, per hdiutil pmap, partition
0 is the partition map itself.
-growonly only allow the image to grow
-shrinkonly only allow the image to shrink
-nofinalgap allow resize to entirely eliminate the trail-
ing free partition in an APM map. Restoring
such images to very old hardware may inter-
fere with booting.
-limits Displays the minimum, current, and maximum
sizes (in 512-byte sectors) for the image.
In addition to any hosted filesystem con-
straints, UDRW images are constrained by
available disk space in the filesystem host-
ing the image. -limits does not modify the
image.
segment
segment -o firstSegname -segmentCount #segs image [opts]
segment -o firstSegname -segmentSize size image [opts]
segment a NDIF or UDIF disk image. Segmented images work
around limitations in file size which are sometimes imposed by
filesystems, network protocols, or media. Note: whether or
not the segments are encrypted is determined by the options
passed to segment and not by the state of the source image.
Common options: -encryption, -stdinpass, -srcimagekey,
-tgtimagekey, -puppetstrings, and -plist.
Options:
-segmentCount segment_count
Specify the number of segments. Only one of
-segmentCount or -segmentSize will be honored.
-segmentSize segment_size
Specify the segment size in sectors or in the
style of mkfile(8) (here unqualified numbers are
still sectors). If the original image size is
not an exact multiple of the segment size, the
last segment will be shorter than the others.
Only one of -segmentCount or -segmentSize will be
honored. Segmenting read/write (UDRW) images is
not supported (as of OS X 10.3).
-firstSegmentSize segment_size
Specify the first segment size in sectors in the
same form as for -segmentSize. Used for multi-CD
restores.
-restricted Make restricted segments for use in multi-CD
restores.
-ov overwrite any existing files.
pmap [options] image
display the partition map of an image or device. By default,
this report includes starting offsets and significant amounts
of free space. image is either a disk image or /dev/disk
entry (see DEVICE SPECIAL FILES).
Common options: -encryption, -stdinpass, -srcimagekey, and
-shadow and related.
-simple generate MediaKit's minimal report: basic parti-
tion types, names, and sizes in human-readable
units.
-standard generate MediaKit's standard report, which adds
partition offsets and uses 512-byte sectors.
-complete generate MediaKit's comprehensive report, with
end offsets, significant free space, etc.
-endoffsets indicate last block of each partition.
-nofreespace suppress all free space reporting. Not valid
with -shims.
-shims report free space < 32 sectors.
-uuids show per-instance UUIDs for each partition. APM
does not store instance UUIDs so these will be
randomly generated for APM maps.
udifrez [options] image
embed resources (e.g. a software license agreement) in a disk
image.
You must specify one of the following options:
-xml file
Copy resources from the XML in file.
-rsrcfork file
Copy resources from file's resource fork.
-replaceall
Delete all pre-existing resources in image.
udifderez [options] image
extract resources from image.
Options:
-xml emit XML output (default)
-rez emit Rez format output
Common options: -encryption, -stdinpass, and -srcimagekey.
EXAMPLES
Verifying:
hdiutil verify myimage.img
verifies an image against its internal checksum.
Segmenting:
hdiutil segment -segmentSize 10m -o /tmp/aseg 30m.dmg
creates aseg.dmg, aseg.002.dmgpart, and aseg.003.dmgpart
Converting:
hdiutil convert master.dmg -format UDTO -o master
converts master.dmg to a CD-R export image named master.cdr
hdiutil convert /dev/disk1 -format UDRW -o devimage
converts the disk /dev/disk1 to a read/write device image
file. authopen(1) will be used if read access to /dev/rdisk1
is not available. Note use of the block-special device.
Burning:
hdiutil burn myImage.dmg
burns the image to optical media and verifies the burn.
hdiutil burn myRawImage.cdr -noverifyburn -noeject
burns the image without verifying the burn or ejecting the
disc. Volumes will be mounted after burning.
Creating a 50 MB encrypted image:
hdiutil create -encryption -size 50m e.dmg -fs HFS+J
Creating a 50 MB encrypted image protected with public key only:
hdiutil create -encryption -size 50m e.dmg -fs HFS+J \
-pubkey F534A3B0C2AEE3B988308CC89AA04ABE7FDB5F30
Creating a 50 MB encrypted image protected with public key and password:
hdiutil create -encryption -size 50m e.dmg -fs HFS+J -agentpass \
-pubkey F534A3B0C2AEE3B988308CC89AA04ABE7FDB5F30
Note that these two -pubkey usage examples assume a certificate corre-
sponding to this public key is currently in the user's keychain or smart
card. For additional information on smart card authorization setup see
sc_auth(8).
Creating an encrypted single-partition image without user interaction:
printf pp|hdiutil create -encryption -stdinpass -size 9m sp.dmg
Creating a "1 GB" SPARSE image (a 1 GB filesystem in a growable file):
hdiutil create -type SPARSE -size 1g -fs HFS+ growableTo1g
Creating a "1 GB" SPARSEBUNDLE (a 1 GB filesystem in a growable bundle):
hdiutil create -type SPARSEBUNDLE -size 1g -fs HFS+ growableTo1g
Creating a new mounted volume backed by an image:
hdiutil create -volname Dick -size 1.3m -fs HFS+ -attach Moby.dmg
Attaching an image on a web server to the system, with any writes going
to a local file:
hdiutil attach http://my.webserver.com/master.dmg -shadow
/tmp/mastershadowfile
Using a shadow file to attach a read-only image read-write to modify it,
then convert it back to a read-only image. This method eliminates the
time/space required to convert a image to read-write before modifying it.
hdiutil attach -owners on Moby.dmg -shadow
/dev/disk2 Apple_partition_scheme
/dev/disk2s1 Apple_partition_map
/dev/disk2s2 Apple_HFS /Volumes/Moby
ditto /Applications/Preview.app /Volumes/Moby
hdiutil detach /dev/disk2
hdiutil convert -format UDZO Moby.dmg -shadow
Creating a RAM-backed device and filesystem.
NUMSECTORS=128000 # a sector is 512 bytes
mydev=`hdiutil attach -nomount ram://$NUMSECTORS`
newfs_hfs $mydev
mkdir /tmp/mymount
mount -t hfs $mydev /tmp/mymount
Using makehybrid to create cross-platform data with files overlapping
between filesystem views. With these files:
albumlist.txt song2.wma song4.m4a song6.mp3 song8.mp3
song1.wma song3.m4a song5.mp3 song7.mp3
hdiutil makehybrid -o MusicBackup.iso Music -hfs -iso -joliet \
-hide-hfs 'Music/*.wma' -hide-joliet 'Music/{*.m4a,*.mp3}' \
-hide-iso 'Music/*.{wma,m4a}'
will create an image with three filesystems pointing to the same blocks.
The HFS+ filesystem, typically only visible on Macintosh systems, will
not include the .wma files, but will show the .m4a and .mp3 files. The
Joliet filesystem will not show the .m4a and .mp3 files, but will show
the .wma files. The ISO9660 filesystem, typically the default filesystem
for optical media on many platforms, will only show the .mp3 files. All
three filesystems will include the "albumlist.txt" files.
Image from directory (new-style):
hdiutil create -srcfolder mydir mydir.dmg
Image from directory (10.1-style; of historical interest):
du -s myFolder # du(1) will count resource forks
10542
hdiutil create -sectors 10642 folder # add ~1% for filesytem
hdid -nomount folder.dmg
...
/dev/disk1s2 Apple_HFS
newfs_hfs -v myFolderImage /dev/rdisk1s2
hdiutil detach disk1
hdid folder.dmg
...
/dev/disk1s2 Apple_HFS /Volumes/myFolderImage
sudo mount -u -t hfs -o perm /dev/disk1s2 /Volumes/myFolderImage
# optionally enable owners; sudo unneeded if manually mounted
ditto -rsrcFork myFolder /Volumes/myFolderImage
hdiutil detach disk1s2 # all done
hdiutil convert -format UDZO -o folder.z.dmg folder.dmg # compress
Manually changing ownership settings of a read-only disk image:
hdiutil attach myimage.dmg
...
/dev/disk1s2 Apple_HFS /Volumes/myVolume
diskutil unmount disk1s2
mkdir /Volumes/myVolume
sudo mount -r -t hfs -o owners /dev/disk1s2 /Volumes/myVolume
# -o owners is the default for manual mounts
Forcing a known image to attach:
hdiutil attach -imagekey diskimage-class=CRawDiskImage myBlob.bar
ENVIRONMENT
The following environment variables affect hdiutil and DiskImages:
com_apple_hdid_verbose
enable -verbose behavior for attach.
com_apple_hdid_debug
enable -debug behavior for attach.
com_apple_hdid_nokernel
similar to -nokernel but works even with, for example, create
-attach.
com_apple_hdid_kernel
attempt to attach in-kernel first (like attach -kernel). In OS
X 10.4.x, in-kernel was the default behavior for UDRW and
SPARSE images. On OS X 10.5, these and other kernel-compati-
ble images, including RAM-based images described in hdid(8),
will attach with a user process unless attach -kernel is used
or the corresponding variable is set. If an image is not
"kernel-compatible" and -kernel is specified, the attach will
fail. (WARNING: ram:// images currently use wired memory when
attached in-kernel).
com_apple_diskimages_insecureHTTP
disable SSL peer verification the same way -insecurehttp does.
Useful for clients of DiskImages such as asr(8) which don't
support a similar command line option.
ERRORS
DiskImages uses many frameworks and can encounter many error codes. In
general, it tries to turn these error numbers into localized strings for
the user. For background, intro(2) is a good explanation of our primary
error domain: the BSD errno values. For debugging, -verbose should gen-
erally provide enough information to figure out what has gone wrong. The
following is a list of interesting errors that hdiutil may encounter:
No mountable filesystems
The "No mountable filesystems" error from hdiutil
attach means that no filesystems could be recognized
or mounted after the disk image was attached. The
default behavior in this case is to detach the disk
image. See attach for options modifying this behav-
ior. This error can occur if the disk image or con-
tained filesystem is corrupt. It can also occur if an
image was created from a block device containing a
mounted, journaled filesystem (in which case the image
contains a dirty journal that can't be replayed with-
out making the image read/write, such as with attach
-shadow).
[ENXIO] Device not configured. This error is returned explic-
itly by DiskImages when its kernel driver or framework
helper cannot be contacted. It also often shows up
when a device has been removed while I/O is still
active. One common case of the helper not being found
is when Foundation's Distributed Objects RPC mechanism
cannot be configured. D.O. doesn't work under dead
Mach bootstrap contexts such as can exist in a reat-
tached screen(1) session. Root users can take advan-
tage of StartupItemContext(8) (in /usr/libexec) to
access the startup item Mach bootstrap context.
[EINVAL] Invalid argument. This error is used in many contexts
and is often a clue that hdiutil's arguments are sub-
tly non-sensical (e.g. an invalid layout name passed
to create -layout).
[EFBIG] File too large. DiskImages reports this error when
attempting to access a disk image over HTTP that is
too large for the server to support access via Range
requests. Segmented images can sometimes be used to
work around this limitation of older HTTP servers.
This error can also occur if an overflow occurs with
an old-style UDIF resource fork.
[EAUTH] Authentication error. Used by DiskImages when
libcurl(3) is unable to verify its SSL peer or when
Security.framework indicates that the user failed to
enter the correct password. See -insecurehttp and
-cacert for more information about verification of SSL
peers.
[EBUSY] Resource busy. Used if necessary exclusive access
cannot be obtained. This error often appears when a
volume can't be unmounted.
[EAGAIN] Resource temporarily unavailable. As of OS X 10.5,
DiskImages uses read/write locks on its image files to
prevent images from being attached on more than one
machine at a time (e.g. over the network). EAGAIN is
returned if the appropriate read or write lock can't
be obtained.
EACCES vs. EPERM EACCES and EPERM are subtly different. The latter
"operation not permitted" tends to refer to an opera-
tion that cannot be performed, often due to an incor-
rect effective user ID. On the other hand, "permis-
sion denied" tends to mean that a particular file
access mode prevented the operation.
USING PERSISTENT SPARSE IMAGES
As of OS X 10.5, a more reliable, efficient, and scalable sparse format,
UDSB (SPARSEBUNDLE), is recommended for persistent sparse images as long
as a backing bundle (directory) is acceptable. OS X 10.5 also introduced
F_FULLFSYNC over AFP (on client and server), allowing proper journal
flushes for HFS+J-bearing images. Critical data should never be stored
in sparse disk images on file servers that don't support F_FULLFSYNC.
SPARSE (UDSP) images and shadow files were designed for intermediate use
when creating other images (e.g. UDZO) when final image sizes are
unknown. As of OS X 10.3.2, partially-updated SPARSE images are properly
handled and are thus safe for persistent storage. SPARSE images are not
recommended for persistent storage on versions of OS X earlier than
10.3.2 and should be avoided in favor of SPARSEBUNDLE images or UDRW
images and resize.
If more space is needed than is referenced by the hosted filesystem,
hdiutil resize or diskutil(8) resize can help to grow or shrink the
filesystem in an image. compact reclaims unused space in sparse images.
Though they request that hosted HFS+ filesystems use a special "front
first" allocation policy, beware that sparse images can enhance the
effects of any fragmentation in the hosted filesystem.
To prevent errors when a filesystem inside of a sparse image has more
free space than the volume holding the sparse image, HFS volumes inside
sparse images will report an amount of free space slightly less than the
amount of free space on the volume on which image resides. The image
filesystem currently only behaves this way as a result of a direct attach
action and will not behave this way if, for example, the filesystem is
unmounted and remounted.
DEVICE SPECIAL FILES
Since any /dev entry can be treated as a raw disk image, it is worth not-
ing which devices can be accessed when and how. /dev/rdisk nodes are
character-special devices, but are "raw" in the BSD sense and force
block-aligned I/O. They are closer to the physical disk than the buffer
cache. /dev/disk nodes, on the other hand, are buffered block-special
devices and are used primarily by the kernel's filesystem code.
It is not possible to read from a /dev/disk node while a filesystem is
mounted from it, but anyone with read access to the appropriate
/dev/rdisk node can use hdiutil verbs such as fsid or pmap with it.
Beware that information read from a raw device while a filesystem is
mounted may not be consistent because the consistent data is stored in
memory or in the filesystem's journal.
The DiskImages framework will attempt to use authopen(1) to open any
device which it can't open (due to EACCES) for reading with open(2).
Depending on session characteristics, this behavior can cause apparent
hangs while trying to access /dev entries while logged in remotely (an
authorization panel is waiting on console).
Generally, the /dev/disk node is preferred for imaging devices (e.g.
convert or create -srcdevice operations), while /dev/rdisk is usable for
the quick pmap or fsid. In particular, converting the blocks of a
mounted journaled filesystem to a read-only image will prevent the volume
in the image from mounting (the journal will be permanently dirty).
PERMISSIONS VS. OWNERS
Some filesystems support permissions including users and groups. While
important for security on a managed filesystem, users and groups ("own-
ers") pose challenges for unmanaged, shared filesystems such as those
typically present in disk images. OS X's solution to this problem is to
make owners optional, both while creating files and enforcing permis-
sions.
By default, unknown HFS filesystems on "external" devices (including disk
images) mount with their owners ignored (mount -o noowners). When owners
are ignored, the system dynamically substitutes the current user's iden-
tify for any owners recorded in the filesystem. When creating new files,
a special UID and GID of _unknown are recorded on the disk. Even if a
filesystem is later mounted with on-disk owners honored, files with
stored UID or GID of _unknown will continue to substitute the current
user's credentials any time the given file is accessed. The net result
is that shared volumes behave as expected even when connected to systems
where their on-disk owners are honored.
On modern OS X systems, root (UID 0) can "see through" the _unknown user
mappings. Thus
sudo ls -l /Volumes/imageVol
will show whatever is really stored in the filesystem (possibly _unknown)
regardless of whether owners are currently being respected on that vol-
ume. In contrast, non-root users will see themselves any time owners are
ignored (either via mount -o noowners or stored _unknown): mary running
ls -l will see that mary owns any owners-ignored filesystems objects
while joe running ls -l on the same objects will see that joe owns them.
Unlike owners, permissions are never optional. A non-writable file will
not be writable just because owners are ignored. However, a file that is
writable by its owner will be writable by everyone if owners are ignored
for that file. Because anyone accessing an owners-ignored file is
treated as the owner, everyone is effectively the owner.
diskutil(8)'s enableOwnership or the Finder's Get Info window can be used
to configure a system to respect the on-disk owners for a filesystem in
the future.
COMPATIBILITY
The DiskImages framework supports a variety of flat-file and dual-fork
image formats, including read/write, read-only, and read-only compressed
(which are decompressed in small chunks as I/O requests are made). It
automatically decodes AppleSingle and MacBinary file formats and is capa-
ble of mounting most images directly from http:// URLs. Because DiskIm-
ages can make many requests over a single connection, responsiveness can
be improved by modifying HTTP server settings such as apache's Max-
KeepAliveRequests and KeepAliveTimeout.
OS X 10.0 supported the disk images of Disk Copy 6 on Mac OS 9. OS X
10.1 added sparse, encrypted, and zlib-compressed images. These images
will not be recognized on OS X 10.0 (or will attach read/write, possibly
allowing for their destruction). As the sparse, shadow, and encrypted
formats have evolved, switches have been added to facilitate the creation
of images that are compatible with older OS versions (at the expense of
the performance and reliability improvements offered by the format
enhancements). In particular, sparse images should not be expected to
attach on versions of OS X older than that which created them.
With OS X 10.2, the most common image formats went "in-kernel" (i.e. the
DiskImages kernel extension served them without a helper process), image
meta-data began being stored both as XML and in the embedded resource
fork, and the default Disk Copy.app "compressed" format became UDZO
(breaking compatibility with 10.0). OS X 10.4 introduced bzip2 compres-
sion in the UDBZ format which provides smaller images (especially when
combined with makehybrid) at the expense of backwards compatibility.
In OS X 10.4.7, the resource forks previously embedded in UDIF images
were abandoned entirely to avoid metadata length limitations imposed by
resource fork structures. As a result, UDIF images created on 10.4.7 and
later will not, by default, be recognized by either OS X 10.1 or OS X
10.0. flatten can be used to customize the type of metadata stored in
the image.
OS X 10.5 introduced sparse bundle images which compact quickly but are
not recognized by previous OS versions. OS X 10.6 removed support for
attaching SPARSEBUNDLE images from network file servers that don't sup-
port F_FULLFSYNC. OS X 10.7 removed double-click support for images using
legacy metadata; these can be rehabilitated using flatten and unflatten,
or simply convert.
HISTORY
Disk images were first invented to electronically store and transmit rep-
resentations of floppy disks for manufacturing replication. These images
of floppies are typically referred to as 'Disk Copy 4.2' images, in ref-
erence to the application that created and restored them to floppy disks.
Disk Copy 4.2 images were block-for-block representations of a floppy
disk, with no notion of compression. DART is a variant of the Disk Copy
4.2 format that supported compression.
NDIF (New Disk Image Format) images were developed to replace the Disk
Copy 4.2 and DART image formats and to support images larger than a
floppy disk. With NDIF and Disk Copy version 6, images could be
"attached" as mass storage devices under Mac OS 9. Apple Data Compres-
sion (ADC) -- which carefully optimizes for fast decompression -- was
used to compress images that were typically created once and restored
many times during manufacturing.
UDIF (Universal Disk Image Format) device images picked up where NDIF
left off, allowing images to represent entire block devices and all the
data therein: DDM, partition map, disk-based drivers, etc. For example,
it can represent bootable CDs which can then be replicated from an image.
To ensure single-fork files (NDIF was dual-fork), it began embedding its
resource fork in the data fork. UDIF is the native image format for OS
X.
Raw disk images from other operating systems (e.g. .iso files) will be
recognized as disk images and can be attached and mounted if OS X recog-
nizes the filesystems. They can also be burned with hdiutil burn.
WHAT'S NEW
OS X 10.7 added the ability to quickly render encrypted images inaccessi-
ble using the new erasekeys verb, which saves time versus securely over-
writing the entire image.
In OS X 10.6, pmap was rewritten to use MediaKit's latest reporting rou-
tines so that it can properly support GPT partition maps. Also -debug
now implies -verbose for all verbs.
OS X 10.5 changed the behavior of attach when run on an existing image or
/dev node: if the image was attached but no volume was mounted, the vol-
ume would be mounted. Prior systems would return the /dev without mount-
ing the volume. This change effectively removes the ability to create a
second /dev node from an existing one.
SEE ALSO
authopen(1), diskutil(8), ditto(8), ioreg(8), drutil(1), msdos.util(8),
hfs.util(8), diskarbitrationd(8),
/System/Library/CoreServices/DiskImageMounter.app.
OS X 16 Aug 2013 OS X
Mac OS X 10.9 - Generated Sat Oct 12 13:10:14 CDT 2013