xzcmp: 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/xzcmp - from package: xz

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

On Debian possible default full paths are:

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

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

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