lrs2lrf: 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/lrs2lrf - from package: calibre

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

Error in other languages:
lrs2lrf: bevel nie gevind nie
lrs2lrf: comandă negăsită
lrs2lrf: comando não encontrado
lrs2lrf: commande introuvable
lrs2lrf: command not found
lrs2lrf: käsku ei ole
lrs2lrf: không tìm thấy lệnh
lrs2lrf: komanda nerasta
lrs2lrf: Kommando nicht gefunden.
lrs2lrf: kommandot finns inte
lrs2lrf: komut yok
lrs2lrf: nie znaleziono polecenia
lrs2lrf: níor aimsíodh an t-ordú
lrs2lrf: no se encontró la orden
lrs2lrf: no s'ha trobat l'ordre
lrs2lrf: opdracht niet gevonden
lrs2lrf: parancs nem található
lrs2lrf: perintah tidak ditemukan
lrs2lrf: príkaz nenájdený
lrs2lrf: příkaz nenalezen
lrs2lrf: команда не найдена
lrs2lrf: командата не е открита
lrs2lrf: 命令找不到
lrs2lrf: コマンドが見つかりません