grpck: 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/grpck - from package: shadow-utils

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

On Debian possible default full paths are:

/usr/sbin/grpck - from package: passwd

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

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