checkpw: 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 Debian possible default full paths are:

/usr/bin/checkpw - from package: checkpw

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

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