|THISCELL(5)||AFS File Reference||THISCELL(5)|
ThisCell - Defines the local cell name
The ThisCell file defines the local cell name. There are two versions of this file, one for a AFS client and one for an AFS server.
The client version of the ThisCell file defines the complete Internet domain-style name (for example, "example.com") of the cell to which the local client machine belongs. It must reside in the /etc/openafs directory on every AFS client machine. To change a client machine's cell membership, edit the file and reboot the machine.
The file is in ASCII format and contains a character string on a single line. The OpenAFS Quick Start Guide instructs the administrator to create it during the installation of each client machine.
The client machine's cell membership determines three defaults important to its functioning:
- The cell in which the machine's users authenticate by default. The effect is two-fold:
- The AFS-modified login utilities and the klog command interpreter contact an Authentication Server in the cell named in the ThisCell file (unless -cell argument to the klog command specifies an alternate cell).
- The command interpreters combine the cell name with the password that the user provides, generating an encryption key from the combination. For authentication to succeed, both the cell name and password must match the ones used to generate the user's encryption key stored in the Authentication Database.
- The cell the Cache Manager considers its local, or home, cell. By default, the Cache Manager allows programs that reside in its home cell to run with setuid permission, but not programs from foreign cells. For more details, see the fs getcellstatus and fs setcell reference pages.
- Which AFS server processes the local AFS command interpreters contact by default as they execute commands issued on the machine.
The client version of the ThisCell file is distinct from the server version, which resides in the /etc/openafs/server directory on each AFS server machine. If a server machine also runs as a client, it is acceptable for the server and client versions of the file on the same machine to name different cells. However, the behavior that results from this configuration can be more confusing than useful.
The server version of the ThisCell file defines the complete Internet domain-style name (for example, "example.com") of the cell to which the server machine belongs. It must reside in the /etc/openafs/server directory on every AFS server machine.
The file is in ASCII format and contains a character string on a single line. The initial version of the file is created with the bos setcellname command during the installation of the cell's first file server machine, and the OpenAFS Quick Start Guide includes instructions for copying it over to additional server machine during their installation.
The only reason to edit the file is as part of changing the cell's name, which is strongly discouraged because of the large number of configuration changes involved. In particular, changing the cell name requires rebuilding the entire Authentication Database, because the Authentication Server combines the cell name it finds in this file with each user and server password and converts the combination into an encryption key before recording it in the Database.
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