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Thread: Persistent udev rules

  1. #1
    Join Date
    Oct 2011
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    Persistent udev rules

    Hi folks!

    I've accidentally deleted the 70-persistent-cd.rules and 70-persistent-net.rules files. For what are these files? How can I recover them since they're not automatically recreated at boot up?


    Many thanks!

  2. #2
    Join Date
    Feb 2011
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    Re: Persistent udev rules

    Those files provide rules for how the kernel should do things.

    Edit (for future reference): The files should recover and populate with a system re-boot. One should not have to re-install udev as I detailed below.

    There may be a better way to do the below, I don't know.

    You should re-install udev. Depending on if udev versions have changed since your first installation, the .deb files might be in the cache. Example:
    First, determine which version you have:
    Code:
    doug@doug-64:/etc/udev/rules.d$ dpkg -l | grep udev
    ii  libudev0                         175-0ubuntu9.2               udev library
    ii  udev                             175-0ubuntu9.2               rule-based device node and kernel event manager
    Then, determine if the .deb is already in the cache:
    Code:
    doug@doug-64:/etc/udev/rules.d$ locate .deb |grep udev
    /var/cache/apt/archives/libudev0_175-0ubuntu9.2_amd64.deb
    /var/cache/apt/archives/udev_175-0ubuntu9.2_amd64.deb
    Good, on my computer it is in the cache, install it:
    Code:
    doug@doug-64:/etc/udev/rules.d$ sudo dpkg -i /var/cache/apt/archives/libudev0_175-0ubuntu9.2_amd64.deb
    (Reading database ... 108384 files and directories currently installed.)
    Preparing to replace libudev0 175-0ubuntu9.2 (using .../libudev0_175-0ubuntu9.2_amd64.deb) ...
    Unpacking replacement libudev0 ...
    Setting up libudev0 (175-0ubuntu9.2) ...
    Processing triggers for libc-bin ...
    ldconfig deferred processing now taking place
    doug@doug-64:/etc/udev/rules.d$ sudo dpkg -i /var/cache/apt/archives/udev_175-0ubuntu9.2_amd64.deb
    (Reading database ... 108384 files and directories currently installed.)
    Preparing to replace udev 175-0ubuntu9.2 (using .../udev_175-0ubuntu9.2_amd64.deb) ...
    Adding 'diversion of /sbin/udevadm to /sbin/udevadm.upgrade by fake-udev'
    Unpacking replacement udev ...
    Setting up udev (175-0ubuntu9.2) ...
    udev stop/waiting
    udev start/running, process 1227
    Removing 'diversion of /sbin/udevadm to /sbin/udevadm.upgrade by fake-udev'
    update-initramfs: deferring update (trigger activated)
    Processing triggers for ureadahead ...
    Processing triggers for man-db ...
    Processing triggers for initramfs-tools ...
    update-initramfs: Generating /boot/initrd.img-3.2.0-33-generic
    O.K. but what if it wasn't in the cache? Go to the package web site and get the .deb files. In my case I would search for "udev" in the precise-updates distribution.
    Last edited by Doug S; November 26th, 2012 at 05:55 PM.

  3. #3
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    Oct 2011
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    Re: Persistent udev rules

    Ok, fine. But new created files are empty and previously weren't.

    Any problem with this?

  4. #4
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    Re: Persistent udev rules

    I have a test machine that I doesn't matter if I mess it up. So I created your exact situation and tried to recover as per what I said above.

    Yes, the files were empty, with only comments after the re-install. However one of them filled out with the proper information when I re-booted the computer. The other one did not, but I think only because I currently have the CD-ROM drive unplugged for another test I was doing (and I forgot to plug it back in).

  5. #5
    Join Date
    Oct 2011
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    Re: Persistent udev rules

    Even after reboot files are empty. Can I simply forget it? Although it doesn't make any sense to have files populated with info if they are not going to be used.

  6. #6
    Join Date
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    Ubuntu 12.04 Precise Pangolin

    Re: Persistent udev rules

    When I plugged in my CD-ROM, that file populated with stuff during the subsequent boot up.

    I don't know for sure, but I assume if your system needed stuff in the files it would have added it during boot up. Unless additionally something else is wrong.

  7. #7
    Join Date
    Oct 2011
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    49

    Re: Persistent udev rules

    Finally I've managed to restore previous rules from a Clonezilla image. I don't know if there will be differences, but I prefer keep things as they are

    For me this is solved. Thanks!

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