svn-fast-backup: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/svn-fast-backup - from package: subversion-tools

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