HOST_ALIASES(5) File Formats Manual HOST_ALIASES(5) NAME host_aliases - Univa Grid Engine host aliases file format DESCRIPTION All Univa Grid Engine components use a hostname resolving service pro- vided by the communication library to identify hosts via a unique host- name. The communication library itself references standard UNIX direc- tory services such as DNS, NIS and /etc/hosts to resolve hostnames. In rare cases these standard services cannot be setup cleanly and Univa Grid Engine communication daemons running on different hosts are unable to automatically determine a unique hostname for one or all hosts which can be used on all hosts. In such situations a Univa Grid Engine host aliases file can be used to provide the communication daemons with a private and consistent hostname resolution database. The communication library is also caching the provided name by the UNIX directory services for at least 10 minutes (default). It is possible to change the re-resolving timeouts with the following sge_qmaster config- uration parameters: DISABLE_NAME_SERVICE_LOOKUP_CACHE NAME_SERVICE_LOOKUP_CACHE_ENTRY_LIFE_TIME NAME_SERVICE_LOOKUP_CACHE_ENTRY_UPDATE_TIME NAME_SERVICE_LOOKUP_CACHE_ENTRY_RERESOLVE_TIME The caching specific parameters are described in sge_conf(5) man page. Changes to the host_aliases file are not immediately active for compo- nents that are already running. If the changes result e.g. in a differ- ent hostname for an execution daemon the daemon must be restarted. At startup of sge_execd or sge_qmaster the database configuration is veri- fied and adjusted. This is also the case if the resulting hostname of the UNIX directory services have changed. If the name of a sge_qmaster or execd host has changed at the UNIX directory services during runtime the running components should be restarted in order to trigger also a verification of the database. Without restart of such daemons the change will be effective once the cached value of the resolved hostname is renewed and it might result in unexpected behavior if previously used hostnames are not resolvable or not unique anymore. Adding new entries without restarting of the sge_qmaster daemon is pos- sible if the resulting hostnames are not influencing the cluster con- figuration. The depending configurations are host configurations, admin host names, execd host names and submit host names. The sge_qmaster daemon will re-read the host_aliases file during runtime from time to time and add some information into the messages logging file. If it would be necessary to restart the sge_qmaster daemon this will also result in a logging in the sge_qmaster messages file. If an already used hostname should be changed either in the directory services or in the host_aliases file without restarting of the sge_qmaster the affected host might be removed from the database first. Once all references to the old hostname are removed and all daemons running on that host have been shut down, the hostname can be changed. Once the hostname has been changed the previous name could still be cached in the communication library or in system services like named. Please make sure that the running sge_qmaster resolves the hostname correctly before adding the renamed host again. This verification could be done with the gethostbyname command mentioned below. Making changes of the behavior of the standard UNIX directory services might also make it necessary to restart affected components. In order to figure out the resulting name of a host at sge_qmaster the gethostbyname option -all_rr could be used (see hostnameutils(1) man page). The location for the host aliases file is //com- mon/host_aliases. FORMAT For each host a single line must be provided with a blank, comma or semicolon separated list of hostname aliases. The first alias is defined to be the unique hostname which will be used by all Univa Grid Engine components using the hostname aliasing service of the communica- tion library. All names used in a single line must be resolvable via UNIX standard directory services. SEE ALSO sge_intro(1), COPYRIGHT See sge_intro(1) for a full statement of rights and permissions. Univa Grid Engine File Formats UGE 8.5.4 HOST_ALIASES(5)