pvfreverse: 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/pvfreverse - from package: mgetty-voice

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

On Debian possible default full paths are:

/usr/bin/pvfreverse - from package: mgetty-pvftools

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

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