spctoppm: 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/spctoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/spctoppm - from package: netpbm

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

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