mp4art: 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 CentOS possible default full paths are:

/usr/bin/mp4art - from package: libmp4v2

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/mp4art - from package: mp4v2-utils

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

Error in other languages:
mp4art: bevel nie gevind nie
mp4art: comandă negăsită
mp4art: comando não encontrado
mp4art: commande introuvable
mp4art: command not found
mp4art: käsku ei ole
mp4art: không tìm thấy lệnh
mp4art: komanda nerasta
mp4art: Kommando nicht gefunden.
mp4art: kommandot finns inte
mp4art: komut yok
mp4art: nie znaleziono polecenia
mp4art: níor aimsíodh an t-ordú
mp4art: no se encontró la orden
mp4art: no s'ha trobat l'ordre
mp4art: opdracht niet gevonden
mp4art: parancs nem található
mp4art: perintah tidak ditemukan
mp4art: príkaz nenájdený
mp4art: příkaz nenalezen
mp4art: команда не найдена
mp4art: командата не е открита
mp4art: 命令找不到
mp4art: コマンドが見つかりません