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Thread: Who is deleting symbolic link in /dev?

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  1. #1
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    Who is deleting symbolic link in /dev?

    I create a symbolic link for /dev/sr0 to cdrom because a library that I use is hardwired to /dev/cdrom. After a reboot, the symbolic link is gone. Who is deleting it, and how can I make him stop?

  2. #2
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    Re: Who is deleting symbolic link in /dev?

    That was me. Sorry.

    In all seriousness, /dev resides only in memory and is created by udev at boot. You'll need to write a startup script to create the symlink if you want it (semi-)permanent. You might be able to add something into udev to do this as well, but I've never monkeyed with it, so I'm blank on the particulars.
    Last edited by BobVila; January 22nd, 2010 at 09:47 PM.

  3. #3
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    Re: Who is deleting symbolic link in /dev?

    Quote Originally Posted by jeffbarish View Post
    I create a symbolic link for /dev/sr0 to cdrom because a library that I use is hardwired to /dev/cdrom. After a reboot, the symbolic link is gone. Who is deleting it, and how can I make him stop?
    Let's try to write an udev rule.

    What's the output of
    Code:
    udevadm info --query=all --name=sr0
    ?

  4. #4
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    Re: Who is deleting symbolic link in /dev?

    Wow. I didn't realize that /dev exists only in memory. No wonder. I'll have to read about udev as it's new to me.

    Here's the output of udevadm:

    $ udevadm info --query=all --name=sr0
    P: /devices/pci0000:00/0000:00:1f.2/host2/target2:0:0/2:0:0:0/block/sr0
    N: sr0
    S: block/11:0
    S: scd0
    S: disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0
    S: cdrom2
    S: cdrw2
    S: dvd2
    S: dvdrw2
    E: UDEV_LOG=3
    E: DEVPATH=/devices/pci0000:00/0000:00:1f.2/host2/target2:0:0/2:0:0:0/block/sr0
    E: MAJOR=11
    E: MINOR=0
    E: DEVNAME=/dev/sr0
    E: DEVTYPE=disk
    E: SUBSYSTEM=block
    E: ID_CDROM=1
    E: ID_CDROM_CD_R=1
    E: ID_CDROM_CD_RW=1
    E: ID_CDROM_DVD=1
    E: ID_CDROM_DVD_R=1
    E: ID_CDROM_DVD_RAM=1
    E: ID_CDROM_MRW=1
    E: ID_CDROM_MRW_W=1
    E: ID_VENDOR=MATSHITA
    E: ID_VENDOR_ENC=MATSHITA
    E: ID_MODEL=DVD-RAM_UJ875AS
    E: ID_MODEL_ENC=DVD-RAM\x20UJ875AS\x20
    E: ID_REVISION=1.00
    E: ID_TYPE=cd
    E: ID_BUS=scsi
    E: ID_PATH=pci-0000:00:1f.2-scsi-0:0:0:0
    E: ACL_MANAGE=1
    E: GENERATED=1
    E: DKD_PRESENTATION_NOPOLICY=0
    E: DEVLINKS=/dev/block/11:0 /dev/scd0 /dev/disk/by-path/pci-0000:00:1f.2-scsi-0:0:0:0 /dev/cdrom2 /dev/cdrw2 /dev/dvd2 /dev/dvdrw2


    Hey. Is this also how my network interfaces get named? I've been wondering why they are eth0 or wlan0 on some platforms but eth1 or wlan1 on others. I'd like to find a way to guarantee consistency.

  5. #5
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    Re: Who is deleting symbolic link in /dev?

    Quote Originally Posted by jeffbarish View Post
    Hey. Is this also how my network interfaces get named? I've been wondering why they are eth0 or wlan0 on some platforms but eth1 or wlan1 on others. I'd like to find a way to guarantee consistency.
    Look at this file:
    /etc/udev/rules.d/70-persistent-net.rules

  6. #6
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    Re: Who is deleting symbolic link in /dev?

    Create a new file in /etc/ude/rules.d
    Code:
    gksu gedit /etc/udev/rules.d/99-my-cdrom-rule.rules
    and add this line to the file:
    Code:
    SUBSYSTEM=="block", ENV{ID_CDROM}=="?*", ENV{ID_PATH}=="pci-0000:00:1f.2-scsi-0:0:0:0", SYMLINK+="cdrom", ENV{GENERATED}="1"
    save the file, cross your fingers and reboot.

    http://reactivated.net/writing_udev_rules.html
    Last edited by sisco311; January 22nd, 2010 at 11:06 PM.

  7. #7
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    Re: Who is deleting symbolic link in /dev?

    You got it. Thanks to all.

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