luarocks-admin: 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/luarocks-admin - from package: luarocks

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

On Debian possible default full paths are:

/usr/bin/luarocks-admin - from package: luarocks

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

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