Mac Os x Manual Page - Hdiutil

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This manual page is for Mac OS X version 10.6.6 Choose a version: 10.6.6 Reading manual pages Manual pages are intended as a quick reference for people who already understand a technology. To learn how the manual is organized or to learn about command syntax, read the manual page for manpages(5). For more information about this technology, look for other documentation in the Apple Reference Library. For general information about writing shell scripts, read Shell Scripting Primer.


BSD General Commands Manual


hdiutil -- manipulate disk images (attach, verify, burn, etc) SYNOPSIS hdiutil verb [options] DESCRIPTION hdiutil uses the DiskImages framework to manipulate disk images. verify create convert compact and burn verify, create, convert, compact, burn.

Common verbs include attach detach attach, detach,

The rest of the verbs are currently: help info checksum chpass unflatten flatten imageinfo help, info, checksum, chpass, unflatten, flatten, imageinfo, isencrypted mountvol unmount, plugins udifrez udifderez internet-enable resize segment isencrypted, mountvol, plugins, udifrez, udifderez, internet-enable, resize, segment, makehybrid and pmap makehybrid, pmap. BACKGROUND Disk images are containers that emulate disks. Like disks, they can be partitioned and formatted. Many uses of disk images blur the distinction between the disk image container and its content, but this distinction is critical to understanding disk images. The terms "attach" and "detach" are used to distinguish the way disk images are connected to and disconnected from the system. 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 file structures are understood, the associated volumes will mount and appear in the Finder. Always consider whether a "disk image" operation applies to the blocks of the disk image device or to the (often file-oriented) content of the image. For example, verify verifies that the blocks stored in a read-only disk image have not changed since it was created. On the other hand, create -srcfolder creates a disk image container, puts a filesystem in it, and then copies the specified files to the new filesystem. 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 operation failed. At a minimum, the probing of any specified images will be detailed. -quiet close stdout and stderr, leaving only hdiutil hdiutil's exit status to indicate success or failure. -debug and -verbose disable -quiet -quiet. be very verbose. This option is good if a large amount of progress information is needed. of Mac OS X 10.6, -debug enables -verbose -verbose. As


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.


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 hdiutil's progress should use -puppetstrings -puppetstrings.

-srcimagekey key=value specify a key/value pair for the disk image recognition system. a synonym) -tgtimagekey key=value specify a key/value pair for any image created. is no input image).

(-imagekey is normally -imagekey

(-imagekey is only a synonym if there -imagekey

-encryption [AES-128|AES-256] specify a particular type of encryption or, if not specified, the default encryption algorithm. The default algorithm is the AES cipher 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). -stdinpass replaces -passphrase though the latter is still supported for compatibility. Beware that the password will contain any newlines before the NULL. See EXAMPLES. 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 DERencoded 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 hexadecimal 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 processed by c_rehash(1). See also --capath and --cacert in curl(1). 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 -shadow, -cacert, -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. passed in any order. A sector is 512 bytes. help display minimal usage information for each verb. usage information for that verb.

Arguments to the verbs can be

hdiutil verb -help will provide basic

attach image [options]

attach image [options] attach a disk image as a device. attach will return information about an already-attached image as if it had attached it. mount is a poorly-named synonym for attach attach. See BACKGROUND. Beware that an image freshly created and attached is treated as a new removable device. hdid(8) and the EXAMPLES section below for more details about how owners are ignored on filesystems on such devices. The output of attach has been stable since OS X 10.0 (though it was is intended to be program-readable. It consists of the /dev node, a applicable), another tab, and a mount point (if any filesystems were tent hints are derived from the partition data, GUID Partition Table Common GUIDs such as "48465300-0000-11AA-AA11-0030654" are mapped to counterparts (here "Apple_HFS"). See

called hdid(8) then) and tab, a content hint (if mounted). Because contypes may leak through. their human-readable

Common options: -encryption -stdinpass -recover -imagekey -shadow -puppetstrings and -encryption, -stdinpass, -recover, -imagekey, -shadow, -puppetstrings, -plist -plist. Options: -readonly -readwrite

-nokernel -kernel


force the resulting device to be read-only attempt to override the DiskImages framework'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. attach with a helper process. This is again the default as of OS X 10.5. attempt to attach this image without a helper process; fail if unsupported. Only UDRW, UDRO, UDZO, and UDSP images are supported in-kernel. Encryption and HTTP-backed images are also supported. prevent this image from being detached. Only root can use this option.

-mount required|optional|suppressed indicate whether filesystems in the image should be mounted or not. The default is required (attach will fail if no filesystems mount). attach -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 -mountroot, mkdtemp(3). assuming only one volume, mount it at path instead of in /Volumes. See fstab(5) for ways a system administrator can make particular volumes automatically mount in particular filesystem locations by editing the file /etc/fstab. -union attempt a union mount over the mount point specified by -mountpoint -mountpoint. Union mounts are no longer supported in Mac OS X, so this flag is currently a no-op. -private suppress filesystem mount notifications. -private confuses programs using the Carbon File Manager and should be avoided in favor of -nobrowse -nobrowse. -nobrowse render any volumes invisible in applications 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 attached to the device in the IOKit registry. -mountpoint path The following options have corresponding elements in the preferences domain and thus can be rendered in both the positive and the negative to override 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 compatibility, hdid(8) does not attempt to verify images before attaching them. Preferences keys: skip-verify, skip-verify-remote, skip-verify-locked, skip-previously-verified

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 normally only performed when Safari downloads and attaches an image. 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, read-only volumes are opened in the Finder. -[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 checking before mounting a disk image. By default, only quarantined images (e.g. downloaded from the Internet) that have not previously passed fsck are checked. Preferences key: auto-fsck detach dev_name [-force -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 Arbitration 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. Options: -force eject is a synonym for detach detach.

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 -encryption, -stdinpass, -srcimagekey, -puppetstrings, -plist -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 useful for large sparse images. -sectors sector_count Specify the size of the image file in 512-byte sectors. -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 defragmented) filesystem on the destination. The resulting 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 overridden with -fs -fs. Other size specifiers, such as -size will override the default size calculation based on the source content, -size, 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

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 -fs, -volname, -stretch, -size) invalid and ignored when using -srcdevice -srcdevice. Common options: -encryption -stdinpass -certificate -pubkey -plist -imagekey -encryption, -stdinpass, -certificate, -pubkey, -plist, -imagekey, -tgtimagekey -puppetstrings and -plist -tgtimagekey, -puppetstrings, -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 version 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. is 4K.

The default

-type UDIF|SPARSE|SPARSEBUNDLE -type is particular to create and is used to specify the format of empty read/write images. It is independent 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 bundle. 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 262144 sectors (1 MB to 128 MB). 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 filesystem in the image and by any partition map. compact can reclaim unused bands in sparse images backing HFS+ filesystems. resize will only change the virtual size of a sparse image. See also USING PERSISTENT SPARSE IMAGES below. -fs filesystem where filesystem is one of HFS+, HFS+J (JHFS+), HFSX, JHFS+X, MS-DOS, or UDF. -fs causes a filesystem 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 adjustments: if the image is the wrong size for the specified filesystem, create will fail. -fs is invalid and ignored when using -srcdevice -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 -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'.

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 specified, 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 specified like -size -size. -stretch is invalid and ignored when using -srcdevice -srcdevice. -fsargs newfs_args additional arguments to pass to whatever newfs program is implied by -fs -fs. newfs_hfs(8) has a number of options that can reduce the amount of space needed by the filesystem's data structures. Suppressing the journal with -fs HFS+ and passing arguments such as -c c=64,a=16,e=16 to -fsargs will minimize gaps at the front of the filesystem, allowing resize to squeeze more space from the filesystem. For truly optimal filesystems, use makehybrid 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 entry to be written. `GPTSPUD' creates a similar Scheme map instead. When attached, multiple /dev either slice 1 (GPT) or slice 2 (APM) as the data /dev/disk1s1, /dev/disk1s2). partition map with a single image but with a GUID Partition entries will be created, with partition. (e.g. /dev/disk1,

Unless overridden by -fs the default layout is `GPTSPUD' (PPC systems used `SPUD' -fs, 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 -attach overwrite an existing file. The default is not to overwrite existing files. attach the image after creating it. If no filesystem is specified via -fs the -fs, attach will fail per the default attach -mount required behavior.

Image from source options (for -srcfolder and -srcdevice -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 convert. Options specific to -srcdevice -srcdevice: -segmentSize size_spec Specify that the image should be written in segments no bigger than size_spec (which follows -size conventions). Options specific to -srcfolder -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 permissions present in the source directory. It prompts for authentication if it detects an unreadable file, a file owned by

directory. It prompts for authentication 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 create, provided name. Format is one of: UDRW UDRO UDCO UDZO UDBZ UFBI UDRo UDCo UDTO UDxx UDSP UDSB RdWr Rdxx ROCo Rken DC42 UDIF read/write image UDIF read-only image UDIF ADC-compressed image UDIF zlib-compressed image UDIF bzip2-compressed image (OS X 10.4+ only) UDIF entire image with MD5 checksum UDIF read-only (obsolete format) UDIF compressed (obsolete format) DVD/CD-R master for export UDIF stub image SPARSE (grows with content) SPARSEBUNDLE (grows with content; bundle-backed) NDIF read/write image (deprecated) NDIF read-only image (Disk Copy 6.3.3 format) NDIF compressed image (deprecated) NDIF compressed (obsolete format) 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 specified ala gzip(1). The default compression level is 1 (fastest). Common options: -encryption -stdinpass -certificate -srcimagekey -tgtimagekey -shadow -encryption, -stdinpass, -certificate, -srcimagekey, -tgtimagekey, and related, -puppetstrings and -plist -puppetstrings, -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 segments 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 specified ??b|??k|??m|??g|??t??p|??e like create create's -size flag. -tasks task_count When converting an image into a compressed format, 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 appropriate drive has been found. Common options: -shadow and related, -srcimagekey -encryption -puppetstrings and -stdinpass -srcimagekey, -encryption, -puppetstrings, -stdinpass. Other options: -device -testburn -anydevice

specify a device to use for burning. See -list -list. don't turn on laser (laser defaults to on). explicitly allow burning to devices not qualified by Apple (kept for backwards compatibility 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]verifyburn -[no]addpmap

do [not] verify disc contents after burn.

The default is to verify.

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 filesystem 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 specifying 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 size of an HFS or HFS+ volume to the size of the data contained ume. This option will change what is burned such that the disc different checksum than the image it came from. The default is blocks of the disk image (minus any trailing Apple_Free). reduce the on the volwill have a to burn all

-[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 protection.

-[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. calculate the size of disc required (the size returned is in sectors) without burning anything. 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. erase all sectors of the disc (this usually takes quit a bit longer than -erase -erase). list all burning devices, with OpenFirmware paths suitable for -device -device.



-fullerase -list

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 generated image can later be burned using burn or converted to another read-only format with convert burn, convert. By default, the filesystem will be readable on most modern computing platforms. The generated filesystem is not intended for conversion 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 is 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 partitioned hard disk, respectively. The El Torito options should not be used for data CDs. Filesystem options:

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 filesystem. -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 simultaneously with HFS+, and requires the presence of an ISO9660 filesystem. Joliet supports Unicode filenames, but is only supported on some operating systems. 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 information 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). 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). 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 string (ISO9660/Joliet). Preparer string (ISO9660/Joliet). Publisher string (ISO9660/Joliet). System Identification string (ISO9660/Joliet). Expose Macintosh-specific files (such as .DS_Store) in non-HFS+ filesystems (ISO9660/Joliet). 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). Use El Torito Hard Disk Emulation mode. The image must represent a virtual device with an MBR partition map and a single partition 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). 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). For a No Emulation boot image, load the data at the specified segment address. This options is not recommended, so that the system



-application -preparer -publisher -system-id -keep-mac-specific -eltorito-boot

-hard-disk-boot -no-emul-boot



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 Validation 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, representing 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 command-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 filesystems, unless overridden. If not specified, defaults to the last path component of source. -hfs-volume-name Volume name for just the HFS+ filesystem 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 directories that should not be exposed in the generated filesystems. The string may need to be quoted to avoid shell expansion, and will be passed to glob(3) for evaluation. Although this option cannot be used multiple times, an arbitrarily complex glob expression can be used. A glob expression of files and directories that should not be exposed via the HFS+ filesystem, although the data may still be present for use by other filesystems (HFS+ only). A glob expression of files and directories 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). A glob expression of files and directories 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. A glob expression of files and directories that should not be exposed via the UDF filesystem, although the data may still be present for use by other filesystems (UDF only). A glob expression of objects that should only be exposed in UDF. A glob expression of objects that should only be exposed in ISO. A glob expression of objects that should only be exposed in Joliet. 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. Instead of using command-line parameters, use a standard plist from standard 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".





-only-udf -only-iso -only-joliet -print-size


If a disk image was specified for source, the image will be attached and paths will be evaluated relative to the mountpoint 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 -abstract-file, -bibliography-file, source directory, not a sub-directory, 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 -encryption, -stdinpass, -srcimagekey, -puppetstrings, and -plist -plist. info display information about DiskImages.framework, the disk image driver, and any images that are currently attached. hdiutil info accepts -plist -plist.

checksum image -type type Calculate the specified checksum on the image data, regardless of image type. Common options: -shadow and related, -encryption -stdinpass -encryption, -stdinpass. and -plist -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. actively. -srcimagekey -puppetstrings -srcimagekey, -puppetstrings,

The default is to change the password inter-

Common options: -recover and -srcimagekey -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 -stdinpass. unflatten image unflatten a UDIF disk image, creating an OS 9-style dual-fork image file (no XML metadata). If the resource fork representation of the metadata becomes greater than 16 MB, the operation will fail with error -39 ("End of fork"). Common options: -encryption -stdinpass and -srcimagekey -encryption, -stdinpass, -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 -srcimagekey, -encryption, -stdinpass. Since images are created "flat" by default, flatten is only required if the UDIF has previously been unflatten unflattened.

by default, flatten is only required if the UDIF has previously been unflatten unflattened. Other options: -noxml don't embed XML data for in-kernel attachment. The image will never attach inkernel. -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. As usual, image can be a /dev More entry corresponding to a physical disk. See the NOTE ON DEV ENTRY ACCESS section. detailed information is presented for HFS file systems.

Common options: -encryption -stdinpass -srcimagekey and -shadow and related. -encryption, -stdinpass, -srcimagekey, mountvol dev_name mount the filesystem in dev_name using Disk Arbitration (similar to diskutil(8)'s mount mount). XML output is available from -plist -plist. Note that mountvol (rather than mount though it often mount, works in OS X 10.5 and later) is the correct way to remount a volume after it has been unmounted by unmount unmount. Prior to OS X 10.5, mount attach would treat a /dev entry as a disk image to be attached mount/attach (creating another /dev entry). That behavior was undesirable. unmount volume [-force -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. mountvol will remount a volume that has been unmounted by unmount unmount. Options: -force

unmount filesystem regardless of open files on that filesystem. -f.

Similar to umount

imageinfo image Print out information about a disk image. Common options: -encryption -stdinpass -srcimagekey -shadow and related, and -plist -encryption, -stdinpass, -srcimagekey, -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. printed. Common options: -plist -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 -plist. internet-enable [-yes | -no | -query image -yes] 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 -encryption, -stdinpass, -srcimagekey, -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 behavior is to resize the image container, the partition, and the filesystem within it by aligning the end of the latter with the end of the image.

If it is, additional details are

and the filesystem within it by aligning the end of the latter with the end of the image. On older systems, resize was limited to pre-defined limits that depended on how the filesystem was created. As of OS X 10.4, resize can be used to grow an HFS filesystem within an image to any size supported by HFS and the filesystem hosting the image. resize is often used when a device image needs to be shrunk so that the HFS/HFS+ partition can be converted to CD-R/DVD-R format and still be burned. Note that gaps cannot be reclaimed as resize does not move data. diskutil(8) resize can be used to move filesystem data so that hdiutil resize can make an image barely larger than the data within it. -fsargs can sometimes be used to minimize filesystem gaps in the image contents. resize can grow a filesystem and image within the bounds of the image and filesystem formats (e.g. roughly 2^63 bytes for HFS+ inside of a UDRW on HFS+). 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 -encryption, -stdinpass, -srcimagekey, -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 system, an error will be returned and the partition will not be resized. min automatically determines the smallest possible size. Other options: -imageonly

only resize the image file, not the partition(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 parpmap, tition map itself. -growonly -shrinkonly -nofinalgap only allow the image to grow only allow the image to shrink allow resize to entirely eliminate the trailing free partition in an APM map. Restoring such images to very old hardware may interfere with booting. Displays the minimum, current, and maximum sizes (in 512-byte sectors) for the image. In addition to any hosted filesystem constraints, UDRW images are constrained by available disk space in the filesystem hosting 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 -encryption, -stdinpass, -srcimagekey, -tgtimagekey, -puppetstrings, -plist -plist. Options: -segmentCount segment_count Specify the number of segments. be honored. -segmentSize segment_size

Only one of -segmentCount or -segmentSize will

-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 -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 offsets and significant amounts of free space. image is either a plain or special file (i.e. a /dev/disk entry). See the NOTE ON DEV ENTRY ACCESS below. Common options: -encryption -stdinpass -srcimagekey and -shadow and related. -encryption, -stdinpass, -srcimagekey, -simple -standard -complete generate MediaKit's minimal report: partition types, names, and sizes in human-readable units. generate MediaKit's standard report, which adds partition offsets and uses 512-byte sectors. 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. -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 entries. 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 -rez emit XML output (default) emit Rez format output

Common options: -encryption -stdinpass and -srcimagekey -encryption, -stdinpass, -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

be used if read access to device.

/dev/rdisk1 is not available.

Note use of the block-special

Burning: hdiutil burn myImage.dmg Burns the image to available optical media and verifies hdiutil burn myRawImage.cdr -noverifyburn -noeject Burns the image without verifying the burn or ejecting 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 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

the burn. the disc. Volumes will be

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/ /Volumes/Moby hdiutil detach /dev/disk2 hdiutil convert -format UDZO Moby.dmg -shadow Using makehybrid to create cross-platform data with files overlapping between filesystem views. 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 With

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 ENVIRONMENT The following environment variables affect hdiutil and DiskImages: com_apple_hdid_verbose enable -verbose behavior for attach attach. com_apple_hdid_debug enable -debug behavior for attach attach. com_apple_hdid_nokernel similar to -nokernel but works even with, for example, create -attach -attach. com_apple_hdid_kernel attempt to attach in-kernel first (like attach -kernel -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-compatible 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 errors 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 generally provide enough information to figure out what has gone wrong. The following is a list of interesting errors that hdiutil may encounter: [ENXIO] Device not configured. This error is returned explicitly 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 reattached screen(1) session. Root users can take advantage of StartupItemContext(8) (in /usr/libexec) to access the startup item Mach bootstrap

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 hdiutil's arguments are subtly non-sensical (e.g. an invalid layout name passed to create -layout -layout). File too large. DiskImages uses this error explicitly when attempting to access a disk image over HTTP that is too large for the server to support Range requests. This error can also occur when the Resource fork of an old-style UDIF overflows. 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. Resource busy. Used if necessary exclusive access cannot be obtained. often appears when a volume can't be unmounted. This error





Resource temporarily unavailable. As of OS X 10.5, DiskImages uses reader/writer 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 and EPERM are subtly different. The latter "operation not permitted" tends to refer to an operation that cannot be performed, often due to an incorrect effective user ID. On the other hand, "permission 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 mended for persistent sparse images as long as a backing bundle (directory) is acceptable. OS X also introduced F_FULLFSYNC over AFP (on client and server), allowing proper journal flushes for bearing images. Critical data should never be stored in sparse disk images on file servers that support F_FULLFSYNC.

recom10.5 HFS+Jdon't

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 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. NOTE ON DEV ENTRY ACCESS Since any /dev entry can be treated as a raw disk image, it is worth noting 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. 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). This may 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 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). COMPATIBILITY 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 "compressed" format became UDZO (breaking compatibility with 10.0). OS X 10.4 introduced bzip2 compression in the UDBZ format which provides smaller images (especially when combined with makehybrid at the expense of backwards compatibility. makehybrid) 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 support F_FULLFSYNC. HISTORY Disk images were first invented to electronically store and transmit representations of floppy disks for manufacturing replication. These images of floppies are typically referred to as 'Disk Copy 4.2' images, in reference 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 Compression (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 singlefork 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 recognizes the filesystems. They can also be burned with hdiutil burn burn. WHAT'S NEW In OS X 10.6, pmap was rewritten to use MediaKit's latest reporting routines 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 volume would be mounted. Prior systems would return the /dev without mounting the volume. This change effectively removes the ability to create a second /dev node from an existing one. SEE ALSO authopen(1), hdid(8), diskutil, ditto(8), ioreg(8), drutil(1), ufs.util(8), msdos.util(8), hfs.util(8), diskarbitrationd(8), /usr/sbin/disktool (run with no arguments for usage), /System/Library/CoreServices/ Mac OS X 22 Apr 2009 Mac OS X

Reporting Problems The way to report a problem with this manual page depends on the type of problem:

Content errors Report errors in the content of this documentation with the feedback links below. Bug reports Report bugs in the functionality of the described tool or API through Bug Reporter. Formatting problems Report formatting mistakes in the online version of these pages with the feedback links below. Did this document help you? Yes It's good, but... Not helpful...

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