ffmsindex: 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/ffmsindex - from package: ffmsindex

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