Just to add a note to Kelvins good info. Here are some excerpts from a Cisco doc that really explains Partitions and CSS perfectly;
Understanding Partitions and Calling Search Spaces
A partition comprises a logical grouping of directory numbers (DNs) and route patterns with similar reachability characteristics. Devices that are typically placed in partitions include DNs and route patterns. These entities associate with DNs that users dial. For simplicity, partition names usually reflect their characteristics, such as "NYLongDistancePT," "NY911PT," and so on.
A calling search space comprises an ordered list of partitions that users can look at before users are allowed to place a call. Calling search spaces determine the partitions that calling devices, including IP phones, soft phones, and gateways, can search when attempting to complete a call.
Calling search spaces determine partitions that calling devices search when they are attempting to complete a call.
For example, assume a calling search space named "Executive" includes four partitions: NYLongDistance, NYInternational, NYLocalCall, and NY911. Assume that another calling search space named "Guest" includes two partitions, NY911 and NYLocalCall.
If the Cisco IP Phone that is associated with a phone or line is in the "Executive" calling search space, the search looks at partitions "NYLongDistance," "NYInternationalCall," "NYLocalCall," and "NY911" when it attempts to initiate the call. Users who are calling from this number can place international calls, long-distance calls, local calls, and calls to 911.
If the Cisco IP Phone that is associated with a phone or line is in the "Guest" calling search space, the search looks only at the "NYLocalCall" and "NY911" partitions when it initiates the call. If a user who is calling from this number tries to dial an international number, a match does not occur, and the call cannot be routed.
Guidelines and Tips
Use the following tips and guidelines when setting up partitions and calling search spaces:
Use concise and descriptive names for your partitions. The CompanynameLocationCalltypePT format usually provides a sufficient level of detail and is short enough to enable you to quickly and easily identify a partition. For example, CiscoDallasMetroPT identifies a partition for toll-free inter-LATA (local access and transport area) calls from the Cisco office in Dallas.
To ensure that dialing privileges are uniform for all lines on a given phone, you may configure the calling search space on the IP phone itself and not on the individual lines of the phone. This practice prevents users from choosing another line on the phone to bypass calling restrictions.
When configuring call forward features on an IP phone line, do not choose a calling search space that can reach the PSTN. This practice prevents users from forwarding their IP phone lines to a long-distance number and dialing their local IP phone number to bypass long-distance toll charges.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.