Thomas Schmitt wrote:
Hi,
My later comments of run-to-run inconsistencies with dd and your recommended
tests were all using my home directory.
In this case any dd run with short result file should issue
some error message and/or there should be some hardware
error message in the system logs.
I captured a test run with the script command.
NOTE dd copies exactly same number of records for differently
sized DVDs :{
Result was:
[snip]
]0;richard@debian-8: ~richard@debian-8:~$
]0;richard@debian-8: ~richard@debian-8:~$ N=0
]0;richard@debian-8: ~richard@debian-8:~$
]0;richard@debian-8: ~richard@debian-8:~$ F="JessieDVD"
]0;richard@debian-8: ~richard@debian-8:~$
]0;richard@debian-8: ~richard@debian-8:~$ E='.iso'
]0;richard@debian-8: ~richard@debian-8:~$
]0;richard@debian-8: ~richard@debian-8:~$ while true
do
let N=N+1
echo "Insert medium, wait until blinking ends, press Enter key (or Ctrl+C
to end)"
read dummyvar
blocks=$(expr $(/sbin/isosize /dev/sr0) / 2048)
echo "Block count: "$blocks
echo "Byte count: $(expr $blocks '*' 2048)"
FILENAME=$F$N$E
echo "The output file will be $FILENAME"
echo ""
dd if=/dev/sr0 bs=2048 count=$blocks of=$FILENAME
echo ""
echo "next lines are output of ls and isosize commnds"
ls -l $FILENAME
/sbin/isosize $FILENAME
echo "about to repeat loop"
echo ""
done
Insert medium, wait until blinking ends, press Enter key (or
Ctrl+C to end)
Block count: 1941504
Byte count: 3976200192
The output file will be JessieDVD1.iso
1941504+0 records in
1941504+0 records out
3976200192 bytes (4.0 GB) copied, 876.109 s, 4.5 MB/s
next lines are output of ls and isosize commnds
-rw-r--r-- 1 richard richard 3976200192 Sep 20 13:39 JessieDVD1.iso
3976200192
about to repeat loop
Insert medium, wait until blinking ends, press Enter key (or
Ctrl+C to end)
Block count: 2284052
Byte count: 4677738496
The output file will be JessieDVD2.iso
1941504+0 records in
1941504+0 records out
3976200192 bytes (4.0 GB) copied, 733.727 s, 5.4 MB/s
next lines are output of ls and isosize commnds
-rw-r--r-- 1 richard richard 3976200192 Sep 20 13:52 JessieDVD2.iso
4677738496
about to repeat loop
Insert medium, wait until blinking ends, press Enter key (or
Ctrl+C to end)
^C
]0;richard@debian-8: ~richard@debian-8:~$ exit
Script done on Sat 20 Sep 2014 01:53:32 PM CDT
