pvfspeed: 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/pvfspeed - from package: mgetty-voice

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

On Debian possible default full paths are:

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

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

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