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When I am making an ISO-Image from a disc, according to the MD5-Hash of the created file, there is a difference between the data. They also differ in size. Tested on two completely different devices.

470b6924c8ac02975f816e4bbae019e2  test_dd.iso
470b6924c8ac02975f816e4bbae019e2  test_original.iso
a26665962c1afc4cf73de261959ba33f  test_readom.iso
470b6924c8ac02975f816e4bbae019e2  test_brasero_iso9660.iso
00d73e6b29230b41429357945df529ba  test_brasero_readom.iso


-rw-r--r-- 1 614400 Jan  6 12:02 test_dd.iso
-rw-r--r-- 1 614400 Jan  6 11:53 test_original.iso
-rw-r--r-- 1 524288 Jan  6 12:02 test_readom.iso

Both dd and readom report an input/output error:

"dd if=/dev/cdrom of=test_dd.iso" output:

dd: error reading ‘/dev/cdrom’: Input/output error
1200+0 records in
1200+0 records out
614400 bytes (614 kB) copied, 5.00922 s, 123 kB/s

"readom dev=/dev/cdrom f=test_readom.iso" output:

Read  speed:  4234 kB/s (CD  24x, DVD  3x).
Write speed:  2822 kB/s (CD  16x, DVD  2x).
Capacity: 302 Blocks = 604 kBytes = 0 MBytes = 0 prMB
Sectorsize: 2048 Bytes
Copy from SCSI (1,0,0) disk to file 'test_readom.iso'
end:       302
Errno: 5 (Input/output error), read_g1 scsi sendcmd: no error
CDB:  28 00 00 00 01 00 00 00 2E 00
status: 0x2 (CHECK CONDITION)
Sense Bytes: F0 00 05 00 00 01 2D 0A 00 00 00 00 64 00 00 00
Sense Key: 0x5 Illegal Request, Segment 0
Sense Code: 0x64 Qual 0x00 (illegal mode for this track) Fru 0x0
Sense flags: Blk 301 (valid) 
cmd finished after 0.495s timeout 40s
readom: Input/output error. Cannot read source disk
readom: Retrying from sector 256.
    ..............................................~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~+~~~-~~~
readom: Input/output error. Error on sector 301 not corrected. Total of 1 errors.

Time total: 38.983sec
Read 512.00 kB at 13.1 kB/sec.
Max corected retry count was 0 (limited to 128).
The following 1 sector(s) could not be read correctly:
301

What might be the cause of this?

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1 Answer 1

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dd is unstable in Debian/Ubuntu because it does not have any built-in error checking. Your dd error is not related to your readom error. The latter error is in much later stage.

However, your readom shows that there is one error which seems to be related to my issue in the thread How to copy CDROM with readom in Debian 8.x? I also added comments in the documentation of the used commands in Commandlinefu.

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