mxtar: 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/mxtar - from package: mtools

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

On Debian possible default full paths are:

/usr/bin/mxtar - from package: mtools

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

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