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I need to copy Codonics medical data from CD to ISO. I insert an CDROM in the CD drive TSSTcorp DVD+-RW TS-H653H of my Dell Precision T1600. The system detects and mounts the CD when you insert it in Debian. In copying, dd
fails systematically but readom
is the only successful differential tool. However, cp
also fails so there must be better differential tools in copying CDs to ISO in commandline, related LinuxJournal's article here. Workflow
This is the first release of Debian that utilises the new 'systemd' suite that improves system start up speeds. To install Debian 8.0 simply follow the instruction guide below: To download your iso image of Debian 8.0, simply click this Link: Download Debian 8.0 From this page, there are multiple ways that you can download Debian. The netinst CD here is a small CD image that contains just the core Debian installer code and a small core set of text-mode programs (known as 'standard' in Debian). To install a desktop or other common software, you'll also need either an Internet connection or some other Debian CD/DVD images.
Unmount cdrom
Run copy command as pseudocode
Successful workflow with readom
but some error
Atoponce's command proposal of readom
Its docs
Many like to use 'dd' for creating CD/DVD iso images. This is bad. Very bad. The reason this is, is 'dd' doesn't have any built-in error checking. So, you don't know if you got all the bits or not. As such, it is not the right tool for the job. Instead, 'reaom' (read optical media) from the wodim package is what you should be using. It has built-in error checking. Similarly, if you want to burn your newly creating ISO, stay away from 'dd', and use: wodim -v -eject /path/to/image.iso
Workflow
Output: seems to be correctly copied CDROM to .iso but not sure why the error. Tested CDs: 3.
Unsuccessful cp
workflow
Failed dd
attempts so deprecate dd for the task
I get the following message with the command dd if=/dev/cdrom of=/home/masi/Desktop/image.iso
in Debian
Other failed copy commands with dd
with
bs
andconv
with
conv
only
Testing jc___ profiling proposal successfully
So do instead where non-root works, ensuring that nothing is keeping CDROM busy, and activating filebrowser of the CDROM explicitly
Testing ThomasSchmitt's proposal
I do unsuccessfully by umounting and xorriso
Testing the quality of the output
It seems that the copied ISO file does to have any errors so it should be a complete duplicate of the CD. Do for certainty by looking both file trees
Output: no lines in less
output meaning complete equivalence; I tested also completely different contents where complete difference so the output is the same as expected output in both cases.
System characteristics
I do
dmesg | grep cd
returnsDoing
lsscsi -s
gives
OS: Debian 8.5
Linux kernel: 3.16.0-4-amd64
, the one which comes default in Debin 8.5
Hardware: customer Dell PC 2011 (Dell Precision T1600); customer service tag 1CY515J
CD Drive: default of the Dell PC - TSSTcorp DVD+-RW TS-H653H
Test CDs: one full and one blank
Documentation about CDs in Debian: DiskImage
Differential condition: something wrong in CD drive's drivers
Related threads: readom and dd are creating different ISO-Images, Archiving CDs to ISO from the Command Line, 'dd' to read CD-ROM and its effects (Re: howto verify burn?), dd command to copy a cd to a hard disk - Input/output error where some looping of I/O, ...
1 Answer
I am developer of libburn
and work since a year with about the samesystem as mentioned here. Kernel 3.16 has a few CD regressionstowards 2.6, but the use case of copying data should work fine.
I rather see bit rot here (readom
is unmaintained), user errors(wrong device files, readom on mounted medium), and the 'read-ahead bug' with CD media written with write type Track-At-Once (i/o error).The i/o error could have been caused by a poorly readable medium as well.
In detail:
There is no /dev/scd0
on vanilla Debian 8. Only /dev/sr0
andpossibly symbolic links like /dev/cdrom
, dev/dvd
, ...So all failures with scd0
are trivially explainable.The advise to run wodim -scanbus
is futile without having /dev/scdX
,as wodim
looks only at those addresses.
readom
docs are typically copied from readcd and thus reflectthe peculiar view of the author of cdrecord and readcd.Nevertheless it should work, of course.
For copying from a data CD, a DVD, or a BD medium, dd and cpare well ok.There is few use of dd options conv=sync,notrunc
here.conv=sync
is indeed dangerous with certain data sources as it willinject zeros when the data source delivers less than bs bytes perread operation. (Should never happen with CD and bs=2048
.)
'Input/output error'
is not caused by the copy program but a messagefrom the kernel to those programs. It is normally caused by an errorindication of the drive.
In this special case it turned out to be the classic 'CD read-ahead bug'.The last one or two blocks of a CD (not of DVD or BD) may stay unreadablebecause some drives report one or both Track-At-Once run-out blocks aspart of the payload data, which they are not.
In most cases dd
and cp
on kernel 3.16 deliver all payload blocksbefore they abort by i/o error.For older kernels or unlucky situations, there isthe mkisofs
tradition to add 300 kB of padding when ISOs get produced.If some of these 300 KB are not delivered by the kernel, then this doesnot damage the content of files in the ISO.
If the i/o error had happened before the last two blocks of a CD, thenit would more likely have been caused by poorly readable medium. In thiscase the advice would be to look in dmesg output or /var/log/messages
for reports like:
This was a classic medium error. No software problem.Not even a drive problem on the first hand.
'(Device or resource busy)'
error comes from the attempt to opena device file with open(2)
flag O_EXCL
in its non-portable role forLinux devices. See here for open()
peculiarities on CD burner device files.
mount(8)
has the device open with that flag. Well behaved burn programsshould use the flag too and thus learn when they try to use a mounted orburning drive.
readom
uses it in order to avoid spoiling ongoing burn runs.
So for readom
or burn programs one has to first unmount the medium.The advise to unmount before copying is not mandatory with dd
and cp
.
Answer to question about libburn based data reading:
One could try a dd_rescue-ish command of xorriso
The copy should emerge as file ~/cdrom_copy.iso
.Read errors will be reported and copy attempts will go on with the nextblock. The file ~/cdrom_sector_map
will record the pattern of failedand successful reads. Another read run will load it and then try onlythose blocks which were not yet copied successfully.
A successful run should end by a message like
A run with remaining bad blocks would have 'Media region' lines with'-' characters in the quality column. '+' indicates successfully readintervals of blocks. '0' indicates blocks which were not tried yet.(Between tracks they may stay that way. A CD-ROM is supposed tohave only one track.)
CD Track-At-Once run-out blocks cause '-' quality. If this occurs only atone of the last two blocks of a CD, then most likely all payload blockshave been copied to ~/cdrom_copy.iso
.
If you want to abort this quite stubborn program run then it is betterto do in another shell:
If you kill the process instead, then the sector map will not bewritten and the next run will re-read already copied blocks.
After full success or with only the last one or two blocks missingyou should next test whether no files in the copied ISO point tomissing block addresses.
As superuser (or via sudo
):
which should report this note but no further error messages:
As normal user let tar
read all file and consume the output by wc
:
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which should report no i/o error but only a warning and finally three numbers
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If the CD is readable enough to be mountable, then compare the filesof cdrom_copy.iso
and the CD by creating another mount directory and mount /dev/sr0
:
and then compare both file trees. Pipe the output into less
so that incase of many differences it does not flood your terminal
Empty output indicates no differences.Try with mounting a different CD and you should get lots of messages like
If files with same relative path in both trees have different content you will see messages like
When all is ok, then remove file ~/cdrom_sector_map
so that it cannot keep xorriso
from reading blocks from the next CD to which you have toapply this whole procedure.