ypchsh: 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/bin/ypchsh - from package: yp-tools

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

On Debian possible default full paths are:

/usr/bin/ypchsh - from package: nis

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

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