DVDs

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DVD reading and writing are described at the unix level only, since the process is very inefficient in AIPS.

A DVD-R can hold 4.7 GB. There is no limit to the number of files (tar, FITS) you can write or the size of each file, as long as the total does not exceed 4.7 GB.

You can currently write to DVD on six of the R&G machines: RGLINUX2,4-8.  RTDC1-3 reside in the SMA Control Room (which is locked) and are not available for DVD writing or work at the console. A detailed example (RGLINUX7) of the reading/writing process follows.

A caveat:

Our software can currently write only one track. If you have multiple files, you will need to concatenate them according to the second command in "Prepare to write..." below. When you read them back, they will appear as individual tar or FITS files.


Prepare to write by creating an image of the data:

Say I have four tar files of varying sizes, totaling 4.0 GB. Call them file-1.tar, file-2.tar, file-3.tar, and file-4.tar. To create an image of one (e.g., the first) or all of the files, type either of the following:

mkisofs -R -o file-1.raw file-1.tar mkisofs -R -o four-files.raw file-*.tar


Write the image to DVD:
  1. cdrecord -v -dummy -eject -dao -dev=ATA:1,0,0 four-files.raw
  2. cdrecord -v -eject -dao -dev=ATA:1,0,0 four-files.raw

Note: Do not execute the second command (which does the actual burning), if the first command (-dummy) does not complete successfully. You'll know if you're successful if you get a message such as:

"Track 01: xxxx of xxxx MB written," where the two "xxxx"s are the same number.

Restore files from DVD:
  1. Put DVD in drive.
  2. Log on at console or remotely.
  3. In terminal window, type: mount /dev/dvd cd /dvd Your files should be there, i.e., file-1.tar, file-2.tar, file-3.tar, and file-4.tar.
  4. Copy files to your area, e.g., "cp file-1.tar /home/joe_schmoe/file-1.tar".
  5. Type "eject".

Note: The reading/writing instructions vary slightly from machine to machine due to different operating systems. If you have any trouble, please see one of us.

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