Udev - symlinks

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For ease of server maintenace it is sometimes preferable to use a human readable symlink to a device rather than the some what cryptic computer device names. For example /dev/ups is easier to understand that this device has a UPS attached to it rather than /dev/ttyS0. However any manually entered symlinks do not survive a reboot as udev creates the /dev directory structure at boot time.

You have to get udev to create the symlinks for you. This is straightforward with the use of a custom template.

  1. Create the directory /etc/e-smith/templates-custom/etc/udev/rules.d/10-local.rules and change to it.
  2. Using your favorite text editor create a file with a suitable mnemonic name and content similar to:
    # For <description of symlink>
    KERNEL="<device>", SYMLINK="<name>"
    

    Where:
    <device> is the device name. eg. ttyS0.
    <name> is the name of the symlink. eg. ups.

  3. Expand the template:
    expand-template /etc/udev/rules.d/10-local.rules
    

    This is required as a seperate expansion as this template is not known to SME Server.

Using a template also means that only the template needs to be changed should there be an alteration to the hardware, rather than finding and editing individual application config files.