lp-milestones: 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/bin/lp-milestones - from package: lptools

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

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