xzgrep: 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/xzgrep - from package: xz

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

On Debian possible default full paths are:

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

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

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