On Mon, 27 Nov 2000, Bill Davidsen wrote:
>> Direct CD is just an application. It writes to both CDR and CDRW
>> using the UDF filesystem (packet writing). In the case of CDRW,
>> this allows you to treat a CDRW as a big floppy disk. If you
>> require this functionality, then you MUST use UDF under Linux,
>> and it isn't a finished product. You need a 2.4.0 kernel and
>> maybe some magic.
>
> Thank you for saving me the time to look up the correct terms for the
>packet writing. I'm not sure about the degree of magic needed, the
>2.4.0test10 config (last one I have here) shows:
> # CONFIG_UDF_FS is not set
> # CONFIG_UDF_RW is not set
>so I am guessing that this stuff is now in the kernel at the bleeding
>edge.
Yep, thats right. It is not fully functional though, and write
is marked DANGEROUS.
>It is not clear to me where the line falls between the physical (treat
>the CDRW like a floppy) and the logical (UDF filesystem). I have a
>distinct feeling that I've seen something about using other filesystems
>with packet writing, but I have no idea why this might be desirable.
CDR and CDRW media cannot be written to like magnetic media, so a
filesystem like ext2 will not work R/W on CDRW. In order to have
a CDRW or similar read/write media work logically like a hard
disk or floppy, it needs a special filesystem that looks to the
world like it is a normal r/w filesystem, however, behind the
scenes it is merely adding new "packets" to the existing disk
until it is full. A packet can make a previous file appear to
disappear, etc. I believe once it is full, the software does
some sort of garbage collection, but that is where my knowledge
of UDF is weak.
>> I'd just stick to using CDRW's like eraseable CDR's.
>
> So would I, but I don't try to use them for information exchange. As
>noted in the following, there may be more of a problem, because it
>sounds as if one application is using UDF and one isn't, yet another
>issue. I don't know if there's going to be ANY easy answer in Linux for
>that.
Yes, that sounds very plausable. I'd suggest that one piece of
software be standardized on, even a non-linux one, as long as it
does the job until Linux can play nice with it too.
>> >The difficult story began when I recently purchase a new CDWriter. It does
>> >not support DirectCD but only running Nero therefore I am compelled to
>> >maintain 3 machines with 3 CDWriters, one on M$Win98 with DirectCD, another
>> >on M$Win98 with Nero and another on Linux with CDRoast. The CDRW created
>> >with DirectCD could not be read on the machine running Nero and vice versa
>> >because of different format.
>
> Depending on the state of your disk space and courage, you could run
>WinXX under VMware, WinVM, or whatever and at least get at the data.
Last time I checked, that wouldn't work under VMware. That was
about 8 months ago though. If it does work now, you'd likely
need a very fast system to prevent overruns on writes. I think
it would still be quite risky. An idea though..
>> It all comes down to iso9660 or UDF. iso9660 is supported in
>> Linux (official stable) and UDF is not.
>>
>> >So I am now looking for a solution with a hope from the list because I have
>> >a stock CDRW having data recorded with DirectCD. What I expect is a
>> >solution for cross reading of CDRW created between DirectCD and Nero
>> >respectively
>
> Unfortunately, the is no "stock" CDRW, any more than there is a stock
>floppy. Many formats. If you are willing to go to a development kernel I
>believe you will be able to do UDF, certainly the read, probably the
>write. You can read ISO9660, but you can't read the DirectCD format, so
>in that sense it's not the most widely used format.
I can't say there.. I haven't tried the UDF driver to know how
stable it is, but from what I've heard it is not production ready
by far.
>> I can't help or even guess about DirectCD and Nero as they are
>> applications only, not CD formats. If they both do UDF, and it
>> is compatible with the current devel Linux UDF code, you should
>> be in luck.
>>
>> UDF is what you want in Linux to do what you need. Not an
>> application, but a filesystem driver.
>
> You are probably right about the base format UDF, but I'm not even
>totally convinced of that, given that he can't read between the formats
>and hasn't clarified if he can't see the files or can't read the data.
Perhaps Nero doesn't use UDF, or perhaps it does, but the UDF
implementations between the different software is not the same
and it doesn't work.
> This is a really interesting problem, and I can't tell you how glad I
>am that it's not mine;-)
I certainly agree there. ;o) I just use iso9660 and it works
fine. It's really no less convenient to me.. One can do
multisession until a disk is full, then copy to hd, blank,
remaster, and go again. Not much more difficult than UDF IMHO.
The convenience of UDF IMHO is outweighed by the loss of 150Mb of
disk space... on DVD-RAM however... ;o)
----------------------------------------------------------------------
Mike A. Harris - Linux advocate - Open source advocate
This message is copyright 2000, all rights reserved.
Views expressed are my own, not necessarily shared by my employer.
----------------------------------------------------------------------
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