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| <div style="float: right;">__TOC__</div>
| | See {{man|7|amanda-devices}}. |
| =Introduction=
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| Since release 2.4.3, Amanda supports the usage of a VFS Device, with prefix "file:".
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| As the name suggests, this driver uses files on disk as virtual tapes. Amanda can write to and read from virtual tapes, just like real tapes. A bunch of virtual tapes can even be manipulated with a changer.
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| Possible Uses
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| * Disk-based installations: You can use the file driver to backup onto a set of virtual tapes hosted on a bunch of hard-disks or a RAID-system. Combined with another Amanda configuration that dumps the virtual tapes to real tapes, you can provide reliable backup with faster tapeless recovery. This is called "disk-to-disk-to-tape" backup by some people today.
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| * Inexpensive installations: Without buying a tape drive you can enjoy the benefits of Amanda and backup to a bunch of harddisks. You can create CD/DVD-sized backups which you can burn onto optical disks later. Or you can backup to external disks connected with Firewire or USB.
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| * Test installations: You can easily explore the rich features of Amanda on systems without tape drives. Virtual tapes are usually also much faster than many real tape drives. For a quick start, have a look at: [[Test environment with virtual tapes]].
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| Please be sure to understand the differences between holding disks and virtual tapes. The two serve different purposes; holding disks allow for parallelism of multiple disklist entries (DLE's) being backed up while virtual tapes are a replacement for physical tapes.
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| The virtual tapes are also called "vtapes" in this document.
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| = Using Virtual Tapes =
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| A virtual tape is implemented as a directory with a subdirectory named "data" in it.
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| # chown amanda:disk /amandatapes
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| # chmod 750 /amandatapes # backups contain secret files!
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| # su - amanda
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| $ mkdir -p /amandatapes/test/tape1/data
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| This tape can be manipulated by the [[ammt]] command, a replacement for the system command "mt". The ammt command understands the different output drivers from Amanda:
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| $ ammt -f file:/amandatapes/test/tape1 status
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| $ ammt -f file:/amandatapes/test/tape1 rewind
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| Vtapes are always non-rewinding. Just like Amanda needs them. That's why you always need to rewind it when you want to start reading a vtape from the beginning.
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| Basic writing to a vtape can be done with [[amdd]], a replacement for the system command "dd". Virtual tapes have no real builtin capacity; the upper limit is "diskspace, the final frontier". However Amanda does obey the size you specify in tapetype definition of a vtape in amanda.conf. The amdd command also can specify an upperlimit on the virtual tapesize with the '''-l''' option:
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| $ amdd -l 200k if=/dev/urandom of=file:/amandatapes/test/tape1 bs=32k
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| amdd: write error: No space left on device
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| 8+0 in
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| 6+1 out
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| The above command writes 200 Kbytes of garbage (6 full blocks of 32k + 1 partial block) on the vtape before it bumps into the end of the virtual tape.
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| When there is no "data" subdirectory in a vtape, the vtape is "offline". You could burn the contents of the data directory to a CD-R, and store that away. When you want to read it, just mount is as a "data" directory, or even simpler, create a symlink "data" pointing to the mounted cdrom.
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| $ rm -r /amandatapes/test/tape1/data
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| $ ammt -f file:/amandatapes/test/tape1 status
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| file:/amandatapes/tape1: status: OFFLINE
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| $ ln -s /media/cdrom /amandatapes/test/tape1/data
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| $ ammt -f file:/amandatapes/test/tape1 status
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| file:/amandatapes/test/tape1: status: ONLINE
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| Amanda cannot backup a to CD-R, but can use it as a read protected vtape; making a backup to a vtape, and and later burning the contents of the '''data''' directory to a CD or DVD is the normal way.
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| = See Also =
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| * [[How To:Set Up Virtual Tapes]]
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| = Credit =
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| Based on text by: Stefan G. Weichinger, November - December, 2003 ; minor updates in April, 2005.
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