festival_server: 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/festival_server - from package: festival

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

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