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My OS is Ubuntu 10.10. I have burned Ubuntu 11.04 into a CD. Now I tried to check the CD following, as following:

$ ls -l
-rwxrwx--- 1 root plugdev 718583808 2011-05-19 10:26 ubuntu-11.04-desktop-i386.iso

$ dd if=/dev/cdrom bs=1 count=718583808 | md5sum
dd: reading `/dev/cdrom': Input/output error
718581760+0 records in
718581760+0 records out
718581760 bytes (719 MB) copied5f0528a1b0a834bcf6d25f0b52d97736  -
, 3918.18 s, 183 kB/s

My questions are:

  1. I found my CD appears as /media/Ubuntu 11.04 i386, why not verify it, but to verify /dev/cdrom?
  2. why did I get "dd: reading `/dev/cdrom': Input/output error", and only 718581760 out of 718583808 bytes are processed?
  3. How shall I check the CD then?

Thanks and regards!

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Just boot the CD and from the menu run Check disc for defects:

enter image description here

If everything's ok, you should get the message Check finished: no errors found.

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