xzless: 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/xzless - from package: xz

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

On Debian possible default full paths are:

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

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

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