7.1 From an Exabyte tape

The first step is again to go through the list files in /archive/sw/list and in /archive/sw/list/old to find out on which tape but also on which set the files have been saved (note: the set number can not be one as this set is reserved for the label). If all the files were not saved in the same set, you have to perform the operations below for each different set involved. There are currently a number of Exabyte drives available so you may not want to use the one currently attached to the archive pipeline. If you do, you have to stop the daemon working on this tape (see 3.2.1) to avoid conflicting access. Then insert the tape you want to retrieve files from and rewind it. We suppose here that the device name is /dev/nrst11. The next steps depend on the format used.

7.1.1 TAR format

Position the tape to the correct set number by typing:

mt -t /dev/nrst11 fsf skipnum

where skipnum is the set number minus one. Then extract the files with the tar command. To specify the files you want to retrieve, you may just list them on the command line, for example:

tar xvf /dev/nrst11 194287o.fits 194288o.fits

or you may create a file (ex: readlist) containing one filename per line and use:

tar xvf /dev/nrst11 -I readlist

7.1.2 DUMP format

This format is currently no longer used but it might be necessary to extract files from old tapes. To restore files saved in dump format, you have to be logged as root on the host to which the destination disk is attached. The easiest way is then to use the interactive option of the restore command by typing:

restore ivsf setnum hostdev:/dev/nrst11

where setnum is the set number and hostdev is the name of the host holding the tape device. The tape is positionned and a virtual tree hierarchy, corresponding to the actual tree hierarchy of the disk at time of saving is created. You have to cd through this tree to find the files. For example, with the current archive set-up, the files would have been saved from /archive/dumpexa/.current so you would have to cd to dumpexa/.current. Once on the right virtual directory, the filenames can be list with the ls command. You can specify the files you want to extract by typing add followed by the name of the files you want to extract (add * selects the full set). You can use the add command several times and check that the selected files show a star (*) before their names in the ls list. When the selection is complete, type extract to retrieve the files and specify 1 as the next volume number. When the extraction is complete, refuse any owner and date change and quit restore. Note that the extracted files are not in the current directory but rather in the branch of the tree where they were originaly, that is in our example in ./dumpexa/.current. See figure 7.1 for an example of this procedure. For more information on dump and restore, see the corresponding manpages.

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