cron-deja-vu: 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/cron-deja-vu - from package: cron-deja-vu

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

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