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[exact] --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 checksum information. help and version provide usage and version
information, respectively.
source and target can be /dev entries or volume mountpoints. If restor-
ing 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 mul-
ticast 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 bet-
ter by ditto(1).
asr 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 (includ-
ing 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). Pass-
ing --erase with --file indicates any exist-
ing 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 speci-
fied, 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 writ-
ing 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 try-
ing 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. Skip-
ping verification is dangerous for a number
of reasons and should never be used in pro-
duction systems.
--allowfragmentedcatalog
allows restores to proceed even if the
source's catalog file is fragmented (in par-
ticular, if it has more than 8 extents). By
default such restores are disallowed. Cata-
log 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 impracti-
cal.
--corestorageconvert
Cause target to be converted to a Core Stor-
age LVG at the end of the restore. After
the copy and verify are complete, asr will
create a new Core Storage Logical Volume
Group (LVG), using the partition represented
by target as its only physical volume (PV).
The volume contents restored from source
will be present as a single logical volume
(LV) exported from this LVG. If target is
already a Core Storage LV, then this option
has no effect.
restoreexact performs the same operation as restore, taking all the same
options, but with the following difference: the target
partition is resized to exactly match the size of the
source partition/volume, if such a resize can be done. If
the target partition needs to grow and there is not enough
space, then the operation will fail. If it needs to
shrink, then it should always be able to do so, possibly
leaving free space in the target disk's partition map.
Because the target exactly matches the source in size, all
volume structures should be identical in source and target
upon completion of the restore.
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 multicast-
ing (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 infrastruc-
ture 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 adver-
tised 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 oper-
ation. 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 can-
not 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 cat-
alog 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 perfor-
mance. 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 multi-
plier 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 configuration.plist. The image will not start multicas-
ting on the network until a client attempts to start a restore. The
server will continue to multicast the image until the process is termi-
nated.
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. Click Restore.
BLOCK COPY RESTORE REQUIREMENTS
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 compatibil-
ity. Use -noverify instead.
-blockonly
this option is deprecated, but remains for script compatibil-
ity. 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 opera-
tion. A human readable error message 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, however, leave it unmounted.
Some of the error messages which asr prints are generated by the underly-
ing 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 during 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) may be
transient in nature (e.g. there was an I/O error on the disk), and
it is worth simply trying the restore again.
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 installa-
tion helper application for various Apple computer products. ASR has
been used in manufacturing 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 network stream.
Per its history, most functionality in asr is limited to HFS+ volumes.
SEE ALSO
hdiutil(1), df(1), bless(8), ditto(1), and what(1)
Mac OS X 23 October 2012 Mac OS X
Mac OS X 10.9 - Generated Thu Oct 17 06:26:19 CDT 2013