faust2mathviewer: 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/faust2mathviewer - from package: faust

You may install the required package with command apt-get install {package}
Error in other languages:
faust2mathviewer: bevel nie gevind nie
faust2mathviewer: comandă negăsită
faust2mathviewer: comando não encontrado
faust2mathviewer: commande introuvable
faust2mathviewer: command not found
faust2mathviewer: käsku ei ole
faust2mathviewer: không tìm thấy lệnh
faust2mathviewer: komanda nerasta
faust2mathviewer: Kommando nicht gefunden.
faust2mathviewer: kommandot finns inte
faust2mathviewer: komut yok
faust2mathviewer: nie znaleziono polecenia
faust2mathviewer: níor aimsíodh an t-ordú
faust2mathviewer: no se encontró la orden
faust2mathviewer: no s'ha trobat l'ordre
faust2mathviewer: opdracht niet gevonden
faust2mathviewer: parancs nem található
faust2mathviewer: perintah tidak ditemukan
faust2mathviewer: príkaz nenájdený
faust2mathviewer: příkaz nenalezen
faust2mathviewer: команда не найдена
faust2mathviewer: командата не е открита
faust2mathviewer: 命令找不到
faust2mathviewer: コマンドが見つかりません