fix_filenames.inc: 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
/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/share/ampache/www/bin/fix_filenames.inc - from package: ampache-common

You may install the required package with command apt-get install {package}
Error in other languages:
fix_filenames.inc: bevel nie gevind nie
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fix_filenames.inc: Kommando nicht gefunden.
fix_filenames.inc: kommandot finns inte
fix_filenames.inc: komut yok
fix_filenames.inc: nie znaleziono polecenia
fix_filenames.inc: níor aimsíodh an t-ordú
fix_filenames.inc: no se encontró la orden
fix_filenames.inc: no s'ha trobat l'ordre
fix_filenames.inc: opdracht niet gevonden
fix_filenames.inc: parancs nem található
fix_filenames.inc: perintah tidak ditemukan
fix_filenames.inc: príkaz nenájdený
fix_filenames.inc: příkaz nenalezen
fix_filenames.inc: команда не найдена
fix_filenames.inc: командата не е открита
fix_filenames.inc: 命令找不到
fix_filenames.inc: コマンドが見つかりません