lb: 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/lb - from package: live-build

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

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