xz: 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/xz - from package: xz

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

On Debian possible default full paths are:

/usr/bin/xz - from package: xz-utils

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

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