The yppasswd utility changes the network password associated with the user username in the Network Information Service (NIS) database. If the user has done a keylogin(1), and a publickey/secretkey pair exists
for the user in the NIS publickey.byname map, yppasswd also re-encrypts the secretkey with the new password. The NIS password may be different from the local one on your own machine.
yppasswd prompts for the old NIS password, and then for the new one. You must type in the old password correctly for the change to take effect. The new password must be typed twice, to forestall mistakes.
New passwords must be at least four characters long, if they use a sufficiently rich alphabet, and at least six characters long if monocase. These rules are relaxed if you are insistent enough. Only the owner of the name or the super-user may change a password; superuser on the root master will not be prompted for the old password, and does not need to follow password construction requirements.
The NIS password daemon, rpc.yppasswdd must be running on your NIS server in order for the new password to take effect.