dhcp-lease-list: 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 Debian possible default full paths are:

/usr/sbin/dhcp-lease-list - from package: isc-dhcp-server

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

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