rpc.yppasswdd: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/sbin/rpc.yppasswdd - from package: ypserv

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/sbin/rpc.yppasswdd - from package: nis

You may install the required package with command apt-get install {package}

Error in other languages:
rpc.yppasswdd: bevel nie gevind nie
rpc.yppasswdd: comandă negăsită
rpc.yppasswdd: comando não encontrado
rpc.yppasswdd: commande introuvable
rpc.yppasswdd: command not found
rpc.yppasswdd: käsku ei ole
rpc.yppasswdd: không tìm thấy lệnh
rpc.yppasswdd: komanda nerasta
rpc.yppasswdd: Kommando nicht gefunden.
rpc.yppasswdd: kommandot finns inte
rpc.yppasswdd: komut yok
rpc.yppasswdd: nie znaleziono polecenia
rpc.yppasswdd: níor aimsíodh an t-ordú
rpc.yppasswdd: no se encontró la orden
rpc.yppasswdd: no s'ha trobat l'ordre
rpc.yppasswdd: opdracht niet gevonden
rpc.yppasswdd: parancs nem található
rpc.yppasswdd: perintah tidak ditemukan
rpc.yppasswdd: príkaz nenájdený
rpc.yppasswdd: příkaz nenalezen
rpc.yppasswdd: команда не найдена
rpc.yppasswdd: командата не е открита
rpc.yppasswdd: 命令找不到
rpc.yppasswdd: コマンドが見つかりません