unxz: 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/unxz - from package: xz

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

On Debian possible default full paths are:

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

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

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