luksformat: 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/sbin/luksformat - from package: cryptsetup-bin

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

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