leafpad: 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/leafpad - from package: leafpad

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

On Debian possible default full paths are:

/usr/bin/leafpad - from package: leafpad

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

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