dd: reading `/dev/cdrom': Input/output error

twelvenine · 10-25-2006, 05:02 PM

actually, i have had lots of problems with these cdrws. i bought a pack of 6 like 5 years ago and havent used them all yet, they're made by memorex. the cd in question was unused until i wrote to it yesterday.

i have noticed that older cd's just don't work right sometimes. I have these discs for the pc version of final fantasy VII(from like 1996) and whenever i put them in a cd drive, they get read but it's real slow and the drives make this very loud humming noise. the discs are in great condition(no scratches).

the cd actually works pretty well. i can read it in windows, mount it under linux, and boot from it(bsd boot cd). my output from isofs for the disc is:

Code:

isoinfo -d -i /dev/hdc
CD-ROM is in ISO 9660 format
System id: FreeBSD
Volume id: FreeSBIE
Volume set id: 
Publisher id: 
Data preparer id: 
Application id: MKISOFS ISO 9660/HFS FILESYSTEM BUILDER & CDRECORD CD-R/DVD CREATOR (C) 1993 E.YOUNGDALE (C) 1997 J.PEARSON/J.SCHILLING
Copyright File id: 
Abstract File id: 
Bibliographic File id: 
Volume set size is: 1
Volume set sequence number is: 1
Logical block size is: 2048
Volume size is: 301135
El Torito VD version 1 found, boot catalog is in sector 277361
Joliet with UCS level 3 found
Rock Ridge signatures version 1 found
Eltorito validation header:
    Hid 1
    Arch 0 (x86)
    ID ''
    Key 55 AA
    Eltorito defaultboot header:
        Bootid 88 (bootable)
        Boot media 0 (No Emulation Boot)
        Load segment 0
        Sys type 0
        Nsect 4
        Bootoff 43B79 277369

i've noticed that dd has the i/o error at the same byte every time: 301122. i guess if dd has errors reading the cd, that means the cd is bad, so there's no point in using the ignore errors option and md5sum to check it.

DaneM · 10-25-2006, 09:43 PM

It's possible, as you said, that the CD's bad. It's also possible, however, that it's a problem with the Linux readahead bug. This i/o error is occuring at the very end of the disk. That's where Linux always has the most problems. Most likely, the readahead functionality of the drive is reading right off the end of the medium, which may be what's causing your i/o error. While using conv=notrunc,noerror,sync USUALLY fixes this, it's really only a workaround, and I've seen some CDs (and CD drives) that are just plain stubborn.

If you still have the original CD image, I would suggest burning it using the proper options, as stated in previous posts, and then trying again to md5sum it. Like I've said before, Linux really doesn't like CDs burned in TAO mode.

If you still have problems, let me know and I'll see if I can help you work through them.

--Dane