rsbackup-snapshot-hook: 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/rsbackup-snapshot-hook - from package: rsbackup

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

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