flac: 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 CentOS possible default full paths are:

/usr/bin/flac - from package: flac

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/flac - from package: flac

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

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