lav2yuv: 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/lav2yuv - from package: mjpegtools

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

Error in other languages:
lav2yuv: bevel nie gevind nie
lav2yuv: comandă negăsită
lav2yuv: comando não encontrado
lav2yuv: commande introuvable
lav2yuv: command not found
lav2yuv: käsku ei ole
lav2yuv: không tìm thấy lệnh
lav2yuv: komanda nerasta
lav2yuv: Kommando nicht gefunden.
lav2yuv: kommandot finns inte
lav2yuv: komut yok
lav2yuv: nie znaleziono polecenia
lav2yuv: níor aimsíodh an t-ordú
lav2yuv: no se encontró la orden
lav2yuv: no s'ha trobat l'ordre
lav2yuv: opdracht niet gevonden
lav2yuv: parancs nem található
lav2yuv: perintah tidak ditemukan
lav2yuv: príkaz nenájdený
lav2yuv: příkaz nenalezen
lav2yuv: команда не найдена
lav2yuv: командата не е открита
lav2yuv: 命令找不到
lav2yuv: コマンドが見つかりません