celtenc051: 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 CentOS possible default full paths are:

/usr/bin/celtenc051 - from package: celt051

You may install the required package with command yum install {package}
Error in other languages:
celtenc051: bevel nie gevind nie
celtenc051: comandă negăsită
celtenc051: comando não encontrado
celtenc051: commande introuvable
celtenc051: command not found
celtenc051: käsku ei ole
celtenc051: không tìm thấy lệnh
celtenc051: komanda nerasta
celtenc051: Kommando nicht gefunden.
celtenc051: kommandot finns inte
celtenc051: komut yok
celtenc051: nie znaleziono polecenia
celtenc051: níor aimsíodh an t-ordú
celtenc051: no se encontró la orden
celtenc051: no s'ha trobat l'ordre
celtenc051: opdracht niet gevonden
celtenc051: parancs nem található
celtenc051: perintah tidak ditemukan
celtenc051: príkaz nenájdený
celtenc051: příkaz nenalezen
celtenc051: команда не найдена
celtenc051: командата не е открита
celtenc051: 命令找不到
celtenc051: コマンドが見つかりません