id3tag: 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/id3tag - from package: id3lib

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

On Debian possible default full paths are:

/usr/bin/id3tag - from package: libid3-tools

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

Error in other languages:
id3tag: bevel nie gevind nie
id3tag: comandă negăsită
id3tag: comando não encontrado
id3tag: commande introuvable
id3tag: command not found
id3tag: käsku ei ole
id3tag: không tìm thấy lệnh
id3tag: komanda nerasta
id3tag: Kommando nicht gefunden.
id3tag: kommandot finns inte
id3tag: komut yok
id3tag: nie znaleziono polecenia
id3tag: níor aimsíodh an t-ordú
id3tag: no se encontró la orden
id3tag: no s'ha trobat l'ordre
id3tag: opdracht niet gevonden
id3tag: parancs nem található
id3tag: perintah tidak ditemukan
id3tag: príkaz nenájdený
id3tag: příkaz nenalezen
id3tag: команда не найдена
id3tag: командата не е открита
id3tag: 命令找不到
id3tag: コマンドが見つかりません