amrestore - extract backup images from an Amanda tape
amrestore [ -r | -c | -C ] [ -b blocksize ] [ -p ] [ -h ] tapedevice | holdingfile [ host-
name [ diskname [ datestamp [ hostname [ diskname [ datestamp ... ]]]]]]
Amrestore extracts backup images from the tape mounted on tapedevice or from the holding
disk file holdingfile that match hostname, diskname and datestamp patterns given on the
command line. The tape or holding file must be in a format written by the amdump or
If diskname is not specified, all backups on the tape for the previous hostname are candi-
dates. If datestamp is not specified, all backups on the tape for the previous hostname
and diskname are candidates. If no hostname, diskname or datestamp are specified, every
backup on the tape is a candidate.
Hostname and diskname are special expression descibe in the "HOST & DISK EXPRESSION" sec-
tion of amanda(8). Datestamp are special expression describe in the "DATESTAMP EXPRES-
SION" section of amanda(8). For example, if diskname is "rza", it would match disks
rz2a and rz3a.
Datestamp is useful if amflush writes multiple backup runs to a single tape.
Unless -p is used, candidate backup images are extracted to files in the current directory
-b Set the blocksize used to read the tape or holding file. All holding files must be
read with a blocksize of 32 KBytes. Amrestore should normally be able to determine
the blocksize for tapes on its own and not need this parameter.
The default is 32 KBytes.
-p Pipe output. The first matching backup image is sent to standard output, which is
normally a pipe to restore or tar, then amrestore quits. It may be run again to
continue selecting backups to process. Make sure you specify the no-rewind tapede-
vice when doing this.
Note: restore may report "short read" errors when reading from a pipe. Most ver-
sions of restore support a blocking factor option to let you set the read block
size, and you should set it to 2. See the example below.
-c Compress output using the fastest method the compression program provides. Amre-
store normally writes output files in a format understood by restore or tar, even
if the backups on the tape are compressed. With the -c or -C option, amrestore
writes all files in compressed format, even if the backups on the tape are not com-
pressed. Output file names will have a .Z or .gz extension depending on whether
compress or gzip is the preferred compression program. This option is useful when
the current directory disk is small.
-C Compress output using the best method the compression program provides (may be very
CPU intensive). See the notes above about the -c option.
-r Raw output. Backup images are output exactly as they are on the tape, including
the amdump headers. Output file names will have a .RAW extension. This option is
only useful for debugging and other strange circumstances.
-h Header output. The tape header block is output at the beginning of each file.
This is like -r except -c or -C may also be used to compress the result. Amrecover
uses the header to determine the restore program to use.
If a header is written (-r or -h), only 32 KBytes are output regardless of the tape block-
size. This makes the resulting image usable as a holding file.
The following does an interactive restore of disk rz3g from host seine, to restore partic-
ular files. Note the use of the b option to restore, which causes it to read in units of
two 512-byte blocks (1 Kbyte) at a time. This helps keep it from complaining about short
% amrestore -p /dev/nrmt9 seine rz3g | restore -ivbf 2 -
The next example extracts all backup images for host seine. This is the usual way to
extract all data for a host after a disk crash.
% amrestore /dev/nrmt9 seine
If the backup datestamp in the above example is 19910125 and seine has level 0 backups of
disks rz1a and rz1g on the tape, these files will be created in the current directory:
You may also use amrestore to extract a backup image from a holding disk file that has not
yet been flushed to tape:
% amrestore -p /amanda/20001119/seine.rz1a.2 | restore -ivbf 2 -
Amrestore may be used to generate a listing of images on a tape:
% mt -f /dev/nrmt9 rewind
% amrestore -p /dev/nrmt9 no-such-host > /dev/null
This asks amrestore to find images for host no-such-host. It will not find any entries
that match, but along the way will report each image it skips.
GNU tar must be used to restore files from backup images created with the GNUTAR dumptype.
Vendor tar programs sometimes fail to read GNU tar images.
James da Silva <firstname.lastname@example.org>
University of Maryland, College Park
amanda(8), amdump(8), amflush(8), tar(1) restore(8)