The format utility determines the location of an alternate file by the following methods in this order:
If a file name is given with the format -x option, that file is always used as the data file.
If the -x option is not specified, then the format utility searches the current directory for a file named format.dat. If the file exists, it is used as the data file.
If neither of these methods yields a data file, the format utility uses the /etc/format.dat file as the data file. This file is shipped with the Oracle Solaris OS and should always be present.