viterbi: 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 Debian possible default full paths are:

/usr/bin/viterbi - from package: speech-tools

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

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