debdelta-upgrade: 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/debdelta-upgrade - from package: debdelta

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

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