rsbackup-mount: 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-mount - from package: rsbackup

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

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