yptest: 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/yptest - from package: yp-tools

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

On Debian possible default full paths are:

/usr/sbin/yptest - from package: nis

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

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