flexbackup: 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/flexbackup - from package: flexbackup

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

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