lrf2lrs: 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/lrf2lrs - from package: calibre

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

Error in other languages:
lrf2lrs: bevel nie gevind nie
lrf2lrs: comandă negăsită
lrf2lrs: comando não encontrado
lrf2lrs: commande introuvable
lrf2lrs: command not found
lrf2lrs: käsku ei ole
lrf2lrs: không tìm thấy lệnh
lrf2lrs: komanda nerasta
lrf2lrs: Kommando nicht gefunden.
lrf2lrs: kommandot finns inte
lrf2lrs: komut yok
lrf2lrs: nie znaleziono polecenia
lrf2lrs: níor aimsíodh an t-ordú
lrf2lrs: no se encontró la orden
lrf2lrs: no s'ha trobat l'ordre
lrf2lrs: opdracht niet gevonden
lrf2lrs: parancs nem található
lrf2lrs: perintah tidak ditemukan
lrf2lrs: príkaz nenájdený
lrf2lrs: příkaz nenalezen
lrf2lrs: команда не найдена
lrf2lrs: командата не е открита
lrf2lrs: 命令找不到
lrf2lrs: コマンドが見つかりません