unlz4: 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/unlz4 - from package: lz4

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

Error in other languages:
unlz4: bevel nie gevind nie
unlz4: comandă negăsită
unlz4: comando não encontrado
unlz4: commande introuvable
unlz4: command not found
unlz4: käsku ei ole
unlz4: không tìm thấy lệnh
unlz4: komanda nerasta
unlz4: Kommando nicht gefunden.
unlz4: kommandot finns inte
unlz4: komut yok
unlz4: nie znaleziono polecenia
unlz4: níor aimsíodh an t-ordú
unlz4: no se encontró la orden
unlz4: no s'ha trobat l'ordre
unlz4: opdracht niet gevonden
unlz4: parancs nem található
unlz4: perintah tidak ditemukan
unlz4: príkaz nenájdený
unlz4: příkaz nenalezen
unlz4: команда не найдена
unlz4: командата не е открита
unlz4: 命令找不到
unlz4: コマンドが見つかりません