When using nisbackup, keep in mind that nisbackup is server specific. Regardless of whether or not you use the -a option, nisbackup only backs up those directories that the server you are running it on is master of. NIS+ directory objects that have some other master server will not be backed up.
For example, suppose the submaster1 server is master server for the sales.doc.com. directory objects and also a replica for the west.sales.doc.com. directory objects. When you run nisbackup on submaster1, only the sales.doc.com. directory objects will be backed up.
Some of the implications of this server specific principle are:
Entire NIS+ namespace. If you want to perform an NIS+ back up for an entire multi-domain namespace, and your root master server is also the master server of all subdomains, you can run nisbackup on the root master with the -a option. However, if the root master server is not the master server of all subdomains, you must also run nisbackup on each of the other master servers in order to obtain a complete back up of your entire namespace.
Sub-domains. If you are performing an NIS+ back up for one or more sub-domains, you must run nisbackup on the subdomain's master server. If one machine, such as the root master, is also master of one or more subdomains, you can run nisbackup on that machine with the -a option.
FNS ctx_dir. If you are running FNS, nisbackup will only back up your ctx_dir directories if you run it on the ctx_dir master server and either specify that the ctx_dir be backed up or use the -a option. If, as is common practice, your ctx_dir and NIS+ directory objects are served by different master servers, you must run nisbackup on both machines to back up all directories.