I Have a Tape, and I Don't Know What It Is . . .
From time to time, an administrator is asked to pull data from a tape by a user. Occasionally the user might not know how the tape was created. How do you satisfy this request? First, you can try to use dd to read the first four records of a tape and then try to use file to identify it.
# dd if=/dev/st0 of=/tmp/foo5.out bs=1k count=4 4+0 records in 4+0 records out 4096 bytes (4.1 kB) copied, 0.000115 seconds, 35.6MB/s # file /tmp/foo5.out /tmp/foo5.out: new-fs dump file (little endian), This dump Sat Nov 19 14:37:02 2005, Previous dump Wed Dec 31 19:00:00 1969, Volume 1, Level zero, type: tape header, Label none, Filesystem /work, Device /dev/mapper/vg00-test, Host linux, Flags 3
You can also use file on files of an unknown type in a filesystem.
# file starwatch starwatch: Zip archive data, at least v1.0 to extract # file *gz cllinux: gzip compressed data, was "crossl.tar", from Unix