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Hi I wrote data on a cd. Since then I deleted the isoimage. My questions are : 1) Is it safe to regenerate the deleted isoimage from the cd ? ...
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  1. #1
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    Questions about genisoimage


    Hi

    I wrote data on a cd. Since then I deleted the isoimage. My questions are :
    1) Is it safe to regenerate the deleted isoimage from the cd ? (I guess so, but I don't want my data to be destroyed ; I mean what's the difference for genisoimage to read datas from the hds or from the cds, except for the fs on the device to build the iso file)
    2) Will it be possible to use the -m option again ? (genisoimage /dev/hdc -o /tmp/session1.iso ; genisoimage * -C #,# -m /tmp/session1.iso -o /tmp/session2.iso)
    If you know where I can find the answer, don't be shy to past the link here (I did research, but found nothing)
    Thanks in advance. (In case this information can be useful, I wrote my datas using wodim).

    chris_inx

  2. #2
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    Quote Originally Posted by chris_inx View Post
    1) Is it safe to regenerate the deleted isoimage from the cd ? (I guess so, but I don't want my data to be destroyed ; I mean what's the difference for genisoimage to read datas from the hds or from the cds, except for the fs on the device to build the iso file)
    The CD is read-only, so no worries. The old school dd utility can do this for you. Stick in your CD that you previously created, un-mount it if it is automatically mounted for you, then run something like:

    Code:
    dd if=/dev/cdrom of=/tmp/myimage.iso
    where /dev/cdrom is the proper block device name your kernel uses to address your CD/DVD drive. If not sure, look in demsg.

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    If I use dd, the entire cd will be overwritten again and again, because I do not specify where the last session/next session starts (instead of genisoimage -C last_start,next_start). This may reduce the lifetime of my cd. Also, the data that are already on the cd will be overwritten. Since (not sure) burning operation are not synchronized (reading/writting thread / laser position) I assume that this may lead to corrupted datas.

    Thanks for the help, but for now I will continue using genisoimage/wodim pairs. (I will surely try you way using a rewritable cd one day.).

    chris_inx

  4. #4
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    Quote Originally Posted by chris_inx View Post
    If I use dd, the entire cd will be overwritten again and again
    i thought you wanted to generate an ISO file from the contents on a CD. the dd command reads FROM the CD and writes TO a file on disk.

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    Quote Originally Posted by atreyu View Post
    i thought you wanted to generate an ISO file from the contents on a CD. the dd command reads FROM the CD and writes TO a file on disk.
    Actually, I want to generate an iso file from the cd. As genisoimage provide the -m (merge) option to merge from a previous session (or iso file), I want to know if it will be safe to use genisoimage to regenerate the session1.iso from the cd and to merge it with session2.iso.

    Code:
    # generate iso file from cdrom. (... for omitted parameters)
    genisoimage -o /tmp/session1.iso /media/cdrom0/* ...
    # merge /home/me/* datas AND session1.iso to produce
    # session2.iso
    genisoimage -m /tmp/session1.iso -C #,# -o /tmp/session2.iso  ~/* ...
    # now burn session2.iso on the cd
    wodim ...
    When session2.iso will be generated, I will burn it on the same cd, so that's why I have to be sure before writting that those operations are safe (to avoid overwritting of already burned datas) and by the same time, I will be sure (this time) that I can safely remove session2.iso from the hard disk.

    I do not doubt that
    Code:
    dd if=/dev/hdc of=/tmp/session2.iso
    works fine, but I'm more familiar with genisoimage and I will not try it this time except if you tell me that it's unsafe to regenerate the iso file with genisoimage.

  6. #6
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    ah, okay, now i understand you. I'm not that familiar with genisoimage, so I'm not sure, but here are some tips on doing what you are asking, though, check them out.

    I can tell you what I'd do is just burn a small 2-session CD and then make images and try to write them back to a new CD, one at a time. If that is not your exact procedure, then you know what I mean. Basically...just sacrifice a couple CDs and try it!

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    Atreyu, thanks for the help and for the link. Unfortunately, the link you have pasted uses dax instead of genisoimage. Also, it gives the 'whole' procedure on how-to write a cd. I just want to be sure it is safe to merge 2 iso files when 1 of those has been generated directly from the previous session of a cd. Guess I can't expect much more from you since you are not familiar with genisoimage. Thanks again.

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    Quote Originally Posted by chris_inx View Post
    If you know where I can find the answer, don't be shy to past the link here (I did research, but found nothing)
    ...
    chris_inx
    That's because I assumed the -C option of genisoimage : -M with -C generates an isoimage that will be wrote as a continuation of the previous session ; -M without -C will generates an isoimage that will be wrote as a new session. (Carefull with the last one, specially if wodim -msinfo does not retreive valid numbers that describe the previous session, your datas may be overwritten if the session / disk has not been closed).

    Quote Originally Posted by atreyu View Post
    The CD is read-only, so no worries. The old school dd utility can do this for you. Stick in your CD that you previously created, un-mount it if it is automatically mounted for you, then run something like:

    Code:
    dd if=/dev/cdrom of=/tmp/myimage.iso
    where /dev/cdrom is the proper block device name your kernel uses to address your CD/DVD drive. If not sure, look in demsg.
    Will try it ASAP.

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