红帽全球峰会第 38 章 Adjusting ID ranges manually
An IdM server generates unique user ID (UID) and group ID (GID) numbers. By creating and assigning different ID ranges to replicas, it also ensures that they never generate the same ID numbers. By default, this process is automatic. However, you can manually adjust the IdM ID range during the IdM server installation, or manually define a replica’s DNA ID range.
38.1. ID ranges
ID numbers are divided into ID ranges. Keeping separate numeric ranges for individual servers and replicas eliminates the chance that an ID number issued for an entry is already used by another entry on another server or replica.
Note that there are two distinct types of ID ranges:
- The IdM ID range, which is assigned during the installation of the first server. This range cannot be modified after it is created. However, you can create a new IdM ID range in addition to the original one. For more information, see Automatic ID ranges assignment and Adding a new IdM ID range.
The Distributed Numeric Assignment (DNA) ID ranges, which can be modified by the user. These have to fit within an existing IdM ID range. For more information, see Assigning DNA ID ranges manually.
Replicas can also have a next DNA ID range assigned. A replica uses its next range when it runs out of IDs in its current range. Next ranges are not assigned automatically when a replica is deleted and you must assign them manually.
The ranges are updated and shared between the server and replicas by the DNA plug-in, as part of the back end 389 Directory Server instance for the domain.
The DNA range definition is set by two attributes:
- The server’s next available number: the low end of the DNA range
- The range size: the number of ID’s in the DNA range
The initial bottom range is set during the plug-in instance configuration. After that, the plug-in updates the bottom value. Breaking the available numbers into ranges allows the servers to continually assign numbers without overlapping with each other.
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