cback-span: 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/cback-span - from package: cedar-backup2

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

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