xvminitoppm: 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/xvminitoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/xvminitoppm - from package: netpbm

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

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