leaftoppm: 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/leaftoppm - from package: netpbm-progs

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

On Debian possible default full paths are:

/usr/bin/leaftoppm - from package: netpbm

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

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