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This will write to TAPE (LTO3-4 in my case) a backup of files/folders. Could be changed to write to DVD/Blueray.
Go to the directory where you want to write the output files : cd /bklogs
Enter a name in bkname="Backup1", enter folders/files in tobk="/home /var/www".
It will create a tar and write it to the tape drive on /dev/nst0.
In the process, it will
1) generate a sha512 sum of the tar to $bkname.sha512; so you can validate that your data is intact
2) generate a filelist of the content of the tar with filesize to $bkname.lst
3) buffer the tar file to prevent shoe-shining the tape (I use 4GB for lto3(80mb/sec), 8gb for lto4 (120mb/sec), 3Tb usb3 disks support those speed, else I use 3x2tb raidz.
4) show buffer in/out speed and used space in the buffer
5) show progress bar with time approximation using pv
To eject the tape :
; sleep 75; mt-st -f /dev/nst0 rewoffl
1) When using old tapes, if the buffer is full and the drive slows down, it means the tape is old and would need to be replaced instead of wiping it and recycling it for an other backup. Logging where and when it slows down could provide good information on the wear of the tape. I don't know how to get that information from the mbuffer output and to trigger a "This tape slowed down X times at Y1gb, Y2gb, Y3gb down to Zmb/s for a total of 30sec. It would be wise to replace this tape next time you want to write to it."
2) Fix filesize approximation
3) Save all the output to $bkname.log with progress update being new lines. (any one have an idea?)
4) Support spanning on multiple tape.
5) Replace tar format with something else (dar?); looking at xar right now (https://code.google.com/p/xar/), xml metadata could contain per file checksum, compression algorithm (bzip2, xv, gzip), gnupg encryption, thumbnail, videopreview, image EXIF... But that's an other project.
1) You can specify the width of the progressbar of pv. If its longer than the terminal, line refresh will be written to new lines. That way you can see if there was speed slowdown during writing.
2) Remove the v in tar argument cvf to prevent listing all files added to the archive.
3) You can get tarsum (http://www.guyrutenberg.com/2009/04/29/tarsum-02-a-read-only-version-of-tarsum/)
and add >(tarsum --checksum sha256 > $bkname_list.sha256) after the tee to generate checksums of individual files !
Generate a 18 character password from character set a-zA-Z0-9 from /dev/urandom, pipe the output to Python which prints the password on standard out and in crypt sha512 form.