It seems to me there is a “free support gap” (that is, a gap in free support, not a support gap which is free), for users who are not beginners but are also not master developers—for example, myself. Just about any GNU/Linux question that arises that can be answered by a manpage or googling, I can figure out myself. But for trickier problems (for example, see my null oddity issue from yesterday), there doesn’t seem to be anywhere to go. Most of the helpful subscribers on debian-user are not much more knowledgeable than I am. I run my own linux-disciples list where I can answer most questions but seldom is there anyone to help out with my own questions. Similarly, there is a perl-beginners list, but no “perl-intermediate” or “perl-advanced” list. I’ve also not had much luck writing directly to developers with questions, outside of Debian.

Just a couple cases in point:

  • Using File::Find to follow symlinks — posted to perl beginners, but no response:

    I’d like to use File::Find, or some alternative, to follow symlinks; regardless of whether the file/directory has already been traversed in some other location. In other words, if there I have directories x and y, and the file a is in x and symlinked into y, I want the find &wanted function to be called on file a in both x and y.

    Possible? Do I have to write my own find function from scratch? None of the follow-find=> options seem to accomplish what I want.

    I’ve also noticed that the &wanted function is not called even *once* in some cases where there are duplicate symlink files (i.e., it is not even called on the “real” file). Switching from find to finddepth seems to fix this, but I really don’t understand what’s going on. Any pointers?

    Update: after discussing off-line with a helpful blog reader, I’ve isolated the problem to the following directory structure:

     .: y/ ./y: 1/ 3/ a.jpg ./y/1: a.jpg -> (...full path...)/y/a.jpg ./y/3: 1 -> ../1 

    In other words, a.jpg is in y/. There are two symlinks to that file, one directly — y/1/a.jpg ; the other indirectly, since y/3 contains a symlink to y/1. Perl’s find function only traverses the second instance, not the first. I would like it to do both.

  • growisofs problems — write fails frequently — there doesn’t seem to be any canonical mailing list or support for growisofs, so users are directed to Debian’s cdwrite list:

    I’m using growisofs from dvd+rw-tools from Debian Sarge on an IBM Thinkpad X40 with a DVD writer that reports itself as: “MATSHITADVD-RAM UJ-812.”

    Sometimes I will try 10 or 15 times in a row to burn a DVD and it fails each time with something like:

    :-[ WRITE@LBA=1c970h failed with SK=4h/ASC=03h/ACQ=00h]: Input/output error
    builtin_dd: 117104*2KB out @ average 1.0x1385KBps
    :-( write failed: Input/output error
    /dev/dvd: flushing cache
    /dev/dvd: updating RMA
    /dev/dvd: closing disc
    :-[ CLOSE DISC failed with SK=5h/ASC=72h/ACQ=04h]: Input/output error
    /dev/dvd: reloading tray

    In this example, I had forced the write speed to 1 (it defaults to 2) to see if it makes any difference—it didn’t.

    I would suspect bad media, except that it seems to consistently fail in exactly the same place for a given DVD image to burn. For example, this one keeps failing at 6.13% done. Another failed repeatedly at 47.47%.

    Any ideas what’s going on? Troubleshooting tips? I hate to throw away so many DVDs.

Thus, I throw myself on the mercy of my readers, in particular the Planet Debian crowd. I’ve actually had more luck in the past posting questions to my blog and letting people come to me, rather than seeking out an appropriate forum to ask the question. There seems to something backwards about that.


  1. Ari Pollak Jan 28

    Don’t turn into jwz :(

  2. KDS Jan 28

    I had problems writing DVDs a few months ago when I got I/O errors at around 83%. I got about 5 DVDs before I could find the error. The DVDs (BenQ branded Sony DVDs) had a small “patch” close to its rim and it was that place where growisofs gave me an error. Called up BenQ, explained the problem and got a pack of 50 replacement DVDs from them!

    So check the surface of the media. To see if the image is OK, I would test it on a RW media.

  3. Craig Ringer Jan 28

    I’d suggest testing out cdrecord / dvdrecord if you can. I found that growisofs gave me problems when the same media with the same drive worked just fine with cdrecord.

    If you need the growisofs facilities that’s not much good, but it at least gives you another point to examine in troubleshooting.

  4. Steve Jan 28

    For Perl problems I’ve found to be a wonderful resource.

    I suspect that is the answer to your question in general – rather than asking upon Debian lists instead find a more focussed forum/group to ask your questions in.

    Sometimes this isn’t going to be so useful, but certainly its an option.

  5. Steve Laniel Jan 28



    There is no way to make find or finddepth follow symlinks.

  6. Marc ‘Zugschlus’ Haber Jan 28

    If you can bear the pain of the non-clickable part of the Internet, I’d send you off to good old Usenet. There is still a lot of know-how around there. Use it. Ask smart questions, help others, get helped.

  7. Huub Reuver Jan 28

    It could help if you could tell what type of langauge the DVD-writer uses. CD-record typecally shows what MMC-standard the drive uses (or what cdrecord thinks it should use):
    # cdrecord -checkdrive dev=0,0,0
    Device seems to be: Generic mmc2 DVD-R/DVD-RW.

    The second error is (off course) “Empty or partially written reserved track” (SK=5h/ASC=72h/ACQ=04h) . The other error I can’t find (SK=4h points to hardware errors, but I can’t find SK=4h/ASC=03h/ACQ=00h), MMC2 indicates “controller failure, logical unit failure, parity error, etc.”. With a medium error the sense key should have been 3h.

    General SCSI commands would suggest a “peripheral device write fault”.

    The errors can be found in the mmc-specs:

    The webpage from Andy Polyakov (growisofs) points to this link. I’m not an expert in DVD or SCSI myself, but the tables with error codes are readable. I think the replies in the mailinglist are a little slow due to vacations.

  8. Huub Reuver Jan 28

    One little problem with dvd-drives is you have to use the right media. The right media might depend on the firmware of the drive you use. Especially the older drives needed firmware to be able to use some features and to recognize some raw DVD’s.

    If you have a problem, find out first what media your hardware supplier suggests. And update the firmware if necessary. “it apparently pays off to periodically check for firmware updates” as it says on the growisofs webpage.

  9. mico Jan 28

    I had similar issues until I relized that the computer dealer had used a regular old 40 pin IDE / ATA cable when an UltraATA should’ve been used. I replaced the cable and everything has been smooth since.

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