grpconv: 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/grpconv - from package: shadow-utils

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

On Debian possible default full paths are:

/usr/sbin/grpconv - from package: passwd

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

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