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Tech: Burning a DVD from the FreeBSD command-line
Mon, 18 Jul 2005

Over time, IT folks are virtually guaranteed to complicate everything with a series of nasty acronyms (largely as a form of job security) despite their job description stating something to the effect of "Your job is to reduce complexity of a system." In general, things (be it IT, or automotive, or whatever) tend not to be complex once you catch the lingo, or at least get a feel for whats going on. (A car looked at as a whole is complicated, but a schematic of how the invididual components of a car connect is not, nor is the inner workings of each part.) Likewise with cellphones -- when trying to get your first phone I can guarantee the plethora of terms will throw you for a loop, as it did me -- GPRS, GSM, CDMA, 1xRTT, etc etc -- yet people use cellphones every day. Well, with my new little server having a DVD burner, I figured I'd fire it up and see how many coasters I could make..

(If you're not an IT guy (programmer, sysadmin, etc) or a home Unix hobbyist, you should probably just skip entries I label with things like "FreeBSD" :)

I assembled this new box with some simple but specific goals in mind; naturally, setting it up in the first place required installing an OS, and I really hate installing an OS across the Internet (slow), and no way I'm plugging a floppy drive into this beastie. Installing the initial bits via flash keychain drive is an amusing idea, but really.. I just wanted to get the machine up and going so some form of optical media was needed. (OKay okay, I could've installed across NFS or the net to a LAN PC's copy of the files, but I had ulterior motives..) I've got a number of old CDROM drives around, but they're beige and this machine is black, and really I just wanted to have a DVD burner around, in case I want to make DVDs of my wedding video which is currently VHS only. (Aha, you'll note the wedding video tie in, a great way to make purchases more acceptible to a loving yet penny-pinching spouse :) DVD burners are cheap as coal now, so I picked up a BenQ black mega-slartybart-Fast unit, able to pump out some 8GB of data in 6 minutes or somesuch. Schvoosh! Burning nightly or weekly backups to a multisession DVD would be pretty sweet, and any data that accrues such as .iso rips or the like.. cool stuff.

First step -- acquire blank media.

Uh, erm.. okay, so this sucker can burn regular CDR's and I've got a spingle of them lieing about (10c per blank CDR? Woowoo!), but I want to burn from the command line, and it'd be nice to do DVD here.. not that I can read DVDs in my other machines I just realized ;) Still, burning to CDR and DVD is similar, so lets go to town.. but alas, who knows the difference between DVD-R, DVD+R, DVD-RW, DVD+RW, DVD-RAM, etc etc. Well, so I picked up some cheap DVD-R's, so I can kill them and move on after I figure out why. (Or maybe I'll just burn CDs in the end, since I can read them in my other machines..)

Second step -- make a filesystem/iso to burn

Yep, it is not so simple as just pointing at a directory and uttering the 'please lord, burn me a CD' command - you have to assemble an .iso file and have that burnt to a disk. Fortunately, mkisofs ("mk" "iso" "fs") came with FreeBSD or got installed with one of the ports (though its also available in /usr/ports so no biggy), and I figuered out that this seems to be the incantation: 

mkisofs -o my_iso_filename.iso OPTIONS /my/directory
(where OPTIONS is nothing or could be -R for Rock-Ridge extensions. Again, I forget what all those are but.. Jouliet gets you long filenames and isn't always compatible with all OSes, and Rock Ridge is similar.)

Heres another good one; note that you can list filenames at the end, and thus you could use find to pipe in a list of files that have changed or are in a given path set, etc. I'm also using both -J and -R so the result is Joliet and Rock Ridge, for maximum readability on both Windows and Unix. 

mkisofs -o creature_pit.iso -J -R creature_of_pit_1-HQDivx511.avi creature_of_pit_2-HQDivx511.avi

Third step -- Burn the disk (or create a coaster)

I have learnt that DVD-RAM's need to be formatted prior to use (how about that?), so thats something to keep in mind when you invoke cdrecord or burncd (some googling turned those up. They were in the back of my mind, but I've always just used Nero on a Windows box, so I had to dust off the attic of my mind..) Most people just use a KDE or Gnome or X11 burn frontend or mastering package, but I'd rather just do it from the command line so I can script it for later backups..

Here is a command for (I think) format-and-then-burn-and-finalize, though I'm waiting (forever) to see if it works. I'll try it on a CDR, too, though without the formatting bit: 

burncd -f /dev/acd0 format dvd-rw data creature_from_pit.iso fixate

Hmm, looks like I need to add some ATAPI/CAM drivers into the kernel, so I'll wrap that up another day.. must go to work now :) However, a quick CD burn is easy to do and I needn't apply a kernel change. Prepare the ISO as above and.. 

burncd -f /dev/acd0 data creature_pit.iso fixate

One last thing -- you can also use the old reliable dd to read in a floppy or CD as an .iso image. The following specifies an if and of (in file, out file) and block size:

dd if=/dev/acd0 of=creature-pit.iso bs=2048

Aside: I bet it really annoys some that I alternate between uses of single-dash "-" and double-dash "--" for pauses, titles, etc. (I hyphenate with single-dash of course.) In my brain, I do have a pattern of usage that distinguishes betwixt - and --, but in my rush I'll sometimes be inconsistent. So deal and I'll try to learn how to type someday ;)

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