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ASR(8) BSD System Manager's Manual ASR(8)
NAME
asr -- Apple Software Restore; copy volumes (e.g. from disk images)
SYNOPSIS
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
DESCRIPTION
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
and (optionally) file by file checksum information. help and version provide usage and version infor-mation, information,
mation, 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 accom-plished accomplished
plished by passing a asr:// url as source. By default, asr will restore in place, and will not bless
(see bless(8)) any folders. If --erase is specified, any blessed folders on the source will also be
blessed on the target.
bless -info /Volumes/<vol>
will display current blessed folders for the given volume.
asr generally needs to be run as root (see sudo(8)) 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 filesys-tem filesystem
tem 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 a
erase blockcopy 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 speci-fied specified
fied name. If a directory, the name of the disk image being multicast is
used.
--erase erase erases target and is required if a fast block-copy restore is desired.
By default asr will do a restore-in-place. Duplicate items will not harm
target contents, but files will be replaced. 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.
--updatebless When performing a non-erase restore, --updatebless will update the appropri-ate appropriate
ate information required for the restored volume to boot if the source image
is bootable (equivalent to sudo bless --mount <volume> --setBoot).
--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 pro-gram program
gram 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.
--disableOwners
prevents the default owner-enabling behavior for source and target. Enabling
owners is usually very important for accurate file-by-file copying. In
block-copy restore mode, --disableOwners has no effect.
--wrapper forces an HFS wrapper to be created on the target volume if the --erase
option is used. Normally the creation of a wrapper depends on certain
filesystem variables. --wrapper is ignored if --erase is not used.
--nowrapper forces an HFS wrapper to not be created on the target volume if the --erase
option is used. Normally the creation of a wrapper depends on certain
filesystem variables. --nowrapper is ignored if --erase is not used.
--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 vol-ume volume
ume 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 for-mat. format.
mat. 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 num-
ber 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, multi-cast multicast
cast 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.
--filechecksum
will calculate/store checksum information required to perform file copy
restores. --filechecksum can take a significant amount of time (depending on
the number of files in the image), and will require the user to invoke asr as
root. (see sudo(8) ). Off by default. Note: without file checksums, erase
restores that would degrade from block copy to file copy will instead fail.
--nostream bypasses the check/reordering of a disk image file for multicasting. Off by
default. Disk images will be reordered 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 per-formance. performance.
formance. 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 buffer-ing buffering
ing 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
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. configuration.plist.
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 OS X 10.3. The Disk Copy from
OS X 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. Check "Erase Destination" if you don't need the
target's data. Click Restore.
HOW TO GET THE FASTEST RESTORES
If you are trying to understand file copy (slower) vs. block copy (fast): When you see "Restoring...",
that means the source image volume is larger than the target volume or the volume geometry of the
source image is stretchable to the target size, allowing a high speed block copy to occur. As of OS X
version 10.3, the geometry restrictions have been significantly relaxed such that stretchable source
images are no longer required.
When you see:
Copying "/private/tmp/..." (/dev/diskMsN) to "<target>" (/dev/diskPsQ)...
It means the above is not true, and asr has fallen back to a file copy operation. asr will only block
copy if the volume geometries support it AND you are doing an erase restore. If you are restoring "in
place," a file copy is always performed.
In addition to geometry requirements for supporting block copies, asr requires that the source and des-tination destination
tination filesystems be compatible. A non-HFS+ source can only be used to perform a file copy. 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+.
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. Note that asr will mount the source image as part of verifying its
geometry (see also umount(8) and hdiutil(1) should an image get stuck in this situation). Using
hdiutil(1), particularly the imageinfo, verify, and attach verbs, can help isolate various problems in
accessing the image in question.
HISTORY
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 manufactur-ing manufacturing
ing processes and in shipping computers' System Software Installers.
For Mac OS X, asr was rewritten as a command line tool for manufacturing and professional customers.
asr is the backend for the Mac OS X 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.
SEE ALSO
hdiutil(1), df(1), bless(8), and what(1)
Mac OS X 22 September 2009 Mac OS X
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