Using Vital Product Data For Persistent Device Naming

WhoMartin Schwenke
WhereAUUG 2004 - Who Are You? - Melbourne
WhenSeptember 2004

We discuss an approach to Linux device naming that is similar to the current udev/scsi_id combination. Our approach uses a udev callout, but is much more general than scsi_id. The first time a device is seen, a name is allocated from a sequence in the traditional way. However, this name is remembered by associating it with Vital Product Data (VPD) elements such as manufacturer name, model number and serial number (MF, TM, SN), or a world-wide identifier (WWID), in a database. The approach works for any devices that can be uniquely identified, rather than just SCSI devices. Another advantage of this approach is that new devices do not need to have their names configured before use, so the administrative impact of adding a large number of new devices is quite low. In general, we use (run-parts-style) ordered directories of files to implement naming policy - this approach is known to be useful because system administrators can modify individual files and configuration information can be easily added automatically when installing software packages. Our approach also caters for an arbitrary number of aliases (or symlinks) for each device. One of our naming policies is interesting in that it encodes only the meta-policy - the desired naming policy is built into the database structure, which can be easily changed by renaming or creating new directories.

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