Apple Software Restore; copy volumes (e.g. from disk images.)
Syntax
asr verb [options]
asr restore --source source --target target [options]
asr server --source source --config configuration [options]
asr restore --source asr://source --file file [options]
asr imagescan --source image [options]
asr help | version
asr efficiently copies disk images onto volumes, either directly or via a multicast network stream.
asr can also accurately clone volumes without the use of an intermediate disk image.
In its first form, asr copies source (usually a disk image, potentially on an HTTP server) to target.
source can be specified using a path in the filesystem, or an http or https URL. It can also be an
asr:// URL to indicate a multicast source. asr can also be invoked with its second form to act as a
multicast server. In its third form, asr will restore a multicast disk image to a file instead of disk
volume. In its fourth form, asr prepares a disk image to be restored efficiently, adding whole-volume
checksum information. help and version provide usage and version information, respectively.
source and target can be /dev entries or volume mountpoints. If restoring a multicast disk image to a
file, file can be a path to a local file or directory. If the specified path is a file, the disk image
is given the specified name. If a directory, the name of the disk image being multicast is used. When
specifying server, source has to be a UDIF disk image. Restoring from a multicast stream is accomplished
by passing a asr:// url as source.
When run in its first form above, the --erase option must always be used, as asr no longer supports
file copying. Such functionality is done better by ditto.
asr needs to be run as root (see sudo) in order to accomplish its tasks.
VERBS
Each verb is listed with its description and individual arguments.
restore restores a disk image or volume to another volume (including a mounted disk image)
--source can be a disk image, /dev entry, or volume mountpoint. In the latter two
cases, the volume must be unmountable or mounted read-only in order for a
erase blockcopy to occur (thus, one cannot erase blockcopy the root filesystem
as the source, unless it happened to be mounted read-only).
--target can be a /dev entry, or volume mountpoint. Must be unmountable in order for
an erase block-copy to occur.
--file when performing a multicast restore, --file can be specified instead of
--target. If the specified path is a file, the disk image is given the specified
name. If a directory, the name of the disk image being multicast is
used.
--erase erases target and is required. --erase must always be used, as file copies
are no longer supported by asr. If source is a asr:// url for restoring from
a multicast stream, --erase must be passed (multicasting only supports erase
block-copy restores). Passing --erase with --file indicates any existing
file should be overwritten when doing a multicast file copy.
--format HFS+ | HFSX
specifies the destination filesystem format, when --erase is also given. If
not specified, the destination will be formatted with the same filesystem
format as the source. If multicasting, the --format specified must be block
copy compatible with the source. --format is ignored if --erase is not used.
Note: HFS Journaling is an attribute of the source image, and is not affected
by --format.
--noprompt suppresses the prompt which usually occurs before target is erased.
newfs_hfs(8) will be called on target and once you start writing new data,
there isn’t much hope for recovery. You have been warned.
--timeout num specifies num seconds that a multicast client should wait when no payload
data has been received over a multicast stream before exiting, allowing the
client to stop in case of server failure/stoppage. It defaults to 0 (e.g.
never time out).
--puppetstrings
provide progress output that is easy for another program to parse. Any program
trying to interpret asr’s progress should use --puppetstrings.
--noverify skips the verification steps normally taken to ensure that a volume has been
properly restored. --noverify allows images which have not been scanned to
be restored. Skipping verification is dangerous for a number of reasons and
should never be used in production systems.
--allowfragmentedcatalog
allows restores to proceed even if the source’s catalog file is fragmented
(in particular, if it has more than 8 extents). By default such restores are
disallowed. Catalog fragmentation is undesirable and in most cases it is
better to fix the problem on the source (e.g. by running fsck_hfs -r on it),
but --allowfragmentedcatalog is provided for situations where such a change
is impractical.
server multicasts source over the network. Requires --erase be passed in by clients (multicasting
only supports erase block-copy restores).
--source source has to be a UDIF disk image. A path to a disk image on a local/remote volume
can be passed in, or a http:// url to a disk image that is accessible via a
web server.
--interface
the network interface to be used for multicasting (e.g. en0) instead of the
default network interface.
--config server requires a configuration file to be passed, in standard property list format.
The following keys/options configure the various parameters for multicast
operation.
Required
Data Rate this is the desired data rate in bytes per second. On average, the
stream will go slightly slower than this speed, but will never exceed
it. It’s a number in the plist (-int when set with defaults(1)).
Note: The performance/reliability of the networking infrastructure
being multicast on is an important factor in determining what data
rate can be supported. Excessive/bursty packet loss for a given data
rate could be due to an inability of the server/client to be able to
send/receive multicast data at that rate, but it’s equally important
to verify that the network infrastructure can support multicasting at
the requested rate.
Multicast Address this is the Multicast address for the data stream. It’s a string in
the plist.
Optional
Client Data Rate this is the rate the slowest client can write data to its target in
bytes per second. if asr misses data on the first pass (x’s during
progress) and slowing the Data Rate doesn’t resolve it, setting the
Client Data Rate will dynamically regulate the speed of the multicast
stream to allow clients more time to write the data. It’s a number in
the plist (-int when set with defaults(1)).
DNS Service Discovery whether the server should be advertised via DNS Service Discovery,
a.k.a. Bonjour (tm). It defaults to true. It’s a boolean in the
plist (-bool when set with defaults(1)).
Loop Suspend a limit of the number of times to multicast the image file when no
clients have started a restore operation. Once exceeded, the server
will stop the stream and wait for new clients before multicasting the
image file. It defaults to 0 (e.g. never stop multicasting once a
client starts the stream), and should not be set to <2. It’s a
number in the plist (-int when set with defaults(1)).
Multicast TTL the time to live on the multicast packets (for multicasting through
routers). It defaults to 3. It cannot be set to 0, and should not be
set to 1 (otherwise, it could adversely affect some network routers).
It’s a number in the plist (-int when set with defaults(1)).
Port the port of initial client-server handshake, version checks, multicast
restore metadata, and stream data. It defaults to 7800. This
should only be included/modified if the default port cannot be used.
It’s a number in the plist (-int when set with defaults(1)).
imagescan calculate checksums of the data in the provided image and store them in the image. These
checksums are used to ensure proper restores. Also determines if the disk image is in order
for multicasting, and rewrites the file in order if not. If the image has to be reordered,
it will require free disk space equal to the size of the disk image being scanned.
--nostream
bypasses the check/reordering of a disk image file for multicasting. By default
disk images will be rewritten in a way that’s necessary for multicasting.
--allowfragmentedcatalog
bypasses the check for a fragmented catalog file. By default that check is done
and scanning won’t be allowed on an image that has a fragmented catalog file. It
is usually a better idea to fix the image (e.g. run fsck_hfs -r on a writable copy
of it) than to use --allowfragmentedcatalog, but it is provided in case fixing the
image is impractical.
BUFFERING
The following options control how asr uses memory. These options can have a significant impact on performance.
asr is optimized for copying between devices (different disk drives, from a network volume to a local disk, etc). As such, asr defaults to using eight one megabyte buffers. These buffers are wired down (occupying physical memory). For partition to partition copies on the same device, one large buffer (e.g. 32 MB) is much faster than the default eight medium sized ones. For multicast, 4 256k buffers are the default. Custom buffering for multicast operation is not recommended.
--csumbuffers and --csumbuffersize allow a different buffer configuration for checksumming operations.
One checksum buffer offers the best performance. The default is 1 1MB buffer. Custom checksum buffering
is not recommended.
Like mkfile(8), size defaults to bytes but can be followed by a multiplier character (e.g. 'm').
--buffers num
specifies that num buffers should be used.
--buffersize size
specifies the size of each buffer.
--csumbuffers num
specifies that num buffers should be used for checksumming operations (which only affect
the target). Custom checksum buffering is not recommended.
--csumbuffersize size
specifies the size of each buffer used for checksumming. Custom checksum buffering is not
recommended.
OTHER OPTIONS
--verbose enables verbose progress and error messages.
--debug enables other progress and error messages.
EXAMPLES
Volume cloning:
sudo asr restore --source /Volumes/Classic --target /Volumes/install --erase
Restoring:
sudo asr restore -s compressedimage -t targetvol --erase
Will erase the target and potentially do a block copy restore.
Multicast server:
asr server --source compressedimage --config configuration.plist
Will start up a multicast server for the specified image, using the parameters in the configura-tion.plist.
The image will not start multicasting on the network until a client attempts to start a
restore. The server will continue to multicast the image until the process is terminated.
An example multicast configuration file:
defaults write /tmp/streamconfig "Data Rate" -int 6000000
defaults write /tmp/streamconfig "Multicast Address" mcastaddr
(will create the file /tmp/streamconfig.plist)
mcastaddr should be appropriate for your network infrastructure and policy, usually from a
range assigned by your network administrator.
Multicast client
sudo asr restore --source asr://hostname --target targetvol --erase
Multicast client restoring to a file
sudo asr restore --source asr://hostname --file file --erase
Will receive the multicast stream from hostname and save it to a file. If file is a directory, the
image of the streamed disk image will be used the save the file. --erase causes any existing file with
the same name to be overwritten.
HOW TO USE ASR
asr requires a properly created disk image for most efficient operation. This image is most easily
made with the Disk Utility application’s "Image from Folder" function in macOS 10.3. The Disk Copy from
macOS 10.2.3 (v55.6) or later can also be used.
Basic steps for imaging and restoring a volume:
1. Set up the source volume the way you want it.
2. Use Disk Utility’s "Images -> New -> Image from Folder..." function and select the root of the
volume. Save the image as read-only or compressed. "Images | New | Image from device" is not
recommended on 10.3.x.
3. Scan the image with "Images -> Scan Image for Restore."
4. Select an image or volume and click on the "Restore" tab. Drag the source image and destination
partition to the source and destination fields. Click Restore.
BLOCK COPY RESTORE REQUIRMENTS
asr can block copy restore HFS+/HFSX filesystems and resize the source filesystem to fit in the target’s partition if the source filesystem data blocks will fit within the target partition’s space (resizing the filesystem geometry as appropriate).
HFS+ can be used as the source of a block copy to either an HFS+ or HFSX destination. However, an HFSX source can only be used to block copy to an HFSX destination. This is because case collision of file names could occur when converting from an HFSX filesystem to HFS+.
Certain non-HFS+/HFSX filesystems will block copy restore, but the target partition will be resized to match the size of the source image/partition size, with no filesystem resizing occurring.
COMPATIBILITY
asr maintains compatibility with previous syntax, e.g.
asr -source source -target target [options]
asr -source source -server configuration [options]
asr -source asr://source -file file [options]
asr -imagescan [options] image
asr -h | -v
where -source, -target, and -file are equivalent to --source, --target, and --file respectively, and
all [options] are equivalent to their -- descriptions. asr -server configuration is superseded by asr
server --config configuration. The following deprecated options also remain:
-nocheck this option is deprecated, but remains for script compatibility. Use -noverify instead.
-blockonly
this option is deprecated, but remains for script compatibility. On by default. Note that
if an image scanned with -blockonly cannot be block-copied to a particular target an error
will occur, since the file-copy information was omitted.
Note: Compatibility with previous syntax is not guaranteed in the next major OS release.
ERRORS
asr will exit with status 1 if it cannot complete the requested operation. A human readable error mes-sage message
sage will be printed in most cases. If asr has already started writing to the target volume when the
error occurs, then it will erase the target, leaving it in a valid (but empty) state. It will, how-ever, however,
ever, leave it unmounted.
Some of the error messages which asr prints are generated by the underlying subsystems that it uses,
and their meaning is not always obvious. Here are some useful guidelines:
1. asr does some preflight testing before it starts actually copying data. Errors that show up dur-ing during
ing this preflighting are usually clear (e.g. "There is not enough space in volume "Macintosh HD"
to do the restore.")
2. If an error occurs during the copy, it might be because there is corruption in the source image
file. Try running "hdiutil verify" with the image. A common error message which indicates this
is "codec overrun".
3. Errors which occur during the copy and which don’t have an obvious cause (i.e. the error message
is difficult to interpret) might be transient in nature (e.g. there was an I/O error on the disk),
and it is worth trying the restore again.
Apple Software Restore got its start as a field service restoration tool used to reconfigure computers'
software to 'factory' state. It later became a more general software restore mechanism and software installation helper application for various Apple computer products. ASR has been used in manufacturing processes and in shipping computers' System Software Installers.
For macOS, asr was rewritten as a command line tool for manufacturing and professional customers.
asr is the backend for the macOS Software Restore application that shipped on Macintosh computers as well as the Scan and Restore functionality in Disk Utility.
Multicast support was added to allow multiple clients to erase restore an image from a multicast net-work network
work stream. Per its history, most functionality in asr is limited to HFS+ volumes.
“They always say time changes things, but you actually have to change them yourself” ~ Andy Warhol
Local man page: asr - Command line help page on your local machine.
bless - Set volume bootability and startup disk options.
ditto - Copy files and folders.
df - Display free disk space.
hdiutil - Manipulate iso disk images.
what - show what versions of object modules were used to construct a file.